Category: Integers A sphenic number is a positive integer that is the product of three distinct prime factors. ... A prime number p is called a Sophie Germain prime if 2p + 1 is also prime. ... A triangular number is a number that can be arranged in the shape of an equilateral triangle. ... In number theory, the Mertens function is where μ(k) is the Möbius function. ... A pyramid with side length 5 contains 35 spheres. ... A centered octagonal number is a centered figurate number that represents an octagon with a dot in the center and all other dots surrounding the center dot in successive octagonal layers. ... A safe prime is a prime number of the form 2p + 1, where p is also a prime. ... A centered pentagonal number is a centered figurate number that represents a pentagon with a dot in the center and all other dots surrounding the center in successive pentagonal layers. ... A super-Poulet number is a Poulet number whose every divisor d divides 2d - 2. ... In mathematics, a Woodall number is a natural number of the form n · 2n − 1 (written Wn). ... A decagonal number is a figurate number that represents a decagon. ... In mathematics, a power of two is any of the nonnegative integer powers of the number two; in other words, two times itself a certain number of times. ... The magic constant of a magic square, an n-by-n matrix, is defined such that the sum of any row, column or main diagonal yields the same result, denoted M2(n). ... In mathematics, a magic square of order n is an arrangement of n² numbers in a square, such that the n numbers in all rows, all columns, and both diagonals sum to the same constant. ... 8 {{{67}}} The eight queens puzzle is the problem of putting eight chess queens on an 8×8 chessboard such that none of them is able to capture any other using the standard chess queens moves. ... A pronic number, or oblong number or heteromecic number, is a number which is the product of two consecutive nonnegative integers, that is, n(n + 1). ... In number theory, a branch of mathematics, a highly cototient number k is an integer that has more solutions to the equation x - φ(x) = k, where φ is Eulers totient function, than any integer below it, with the exception of 1. ... A centered heptagonal number is a centered figurate number that represents a heptagon with a dot in the center and all other dots surrounding the center dot in successive heptagonal layers. ... A pyramidal number, or square pyramidal number, is a figurate number that represents a pyramid with a base and four sides. ... 2112 is the fourth studio album by Canadian rock band Rush, released in 1976 (see 1976 in music). ... A nonagonal number or enneagonal number is a figurate number that represents a nonagon. ... A pentagonal pyramidal number is a number equal to the sum of the first few pentagonal numbers. ... A Wedderburn-Etherington number counts how many weakly binary trees can be constructed such that each graph vertex (not counting the root vertex) is adjacent to no more than three other such vertices, for a given number of nodes. ... A vampire number (or true vampire number) is a composite natural number v, with an even number of digits n, that can be factored into two integers x and y each with n/2 digits and not both with trailing zeroes, where v contains all the digits from x and... A Motzkin number for a given number n is the number of different ways of drawing non-intersecting chords on a circle between n points. ... In mathematics, an abundant number or excessive number is a number n for which σ(n) > 2n. ... A Lucas prime is a Lucas number that is prime. ... In mathematics, a Keith number or repfigit number is an integer that appears as a term in a linear recurrence relation with initial terms based off its own digits. ... In mathematics, a Kaprekar number is a number that, in a given base, when squared, can be split into two numbers with the same number of digits as the original number which add up to the original number again. ... An octahedral number is a figurate number that represents an octahedron, or two pyramids placed together, one upside-down underneath the other. ... A cuban prime is a prime number that is a solution to one of two different specific equations involving third powers of x and y. ... A primorial prime is a number that is one less or one more than a primorial and also a prime number. ... For n ≥ 2, the primorial n# is the product of all prime numbers less than or equal to n. ... A centered cube number is a centered figurate number that represents a cube. ... In mathematics, Smarandache-Wellin numbers are special integers; the n-th Smarandache-Wellin number is defined as the concatenation of the first n prime numbers written in decimal notation. ... In mathematics, the Pell numbers and Companion Pell Numbers (Pell-Lucas Numbers) are both sequences of integers. ... The SATs (pronounced S-A-T, not the action sat), formerly called the Scholastic Aptitude Tests and Scholastic Assessment Tests, are standardized tests frequently used by colleges and universities in the United States to aid in the selection of incoming students. ... The magic constant of a magic square, an n-by-n matrix, is defined such that the sum of any row, column or main diagonal yields the same result, denoted M2(n). ... In mathematics, a magic square of order n is an arrangement of n² numbers in a square, such that the n numbers in all rows, all columns, and both diagonals sum to the same constant. ... 8 {{{67}}} The eight queens puzzle is the problem of putting eight chess queens on an 8×8 chessboard such that none of them is able to capture any other using the standard chess queens moves. ... In number theory, a Carmichael number is a composite positive integer n which satisfies the congruence bn − 1 ≡ 1 (mod n) for all integers b which are relatively prime to n (see modular arithmetic). ... A highly composite number is a positive integer which has more divisors than any positive integer below it. ... A Harshad number, or Niven number, is an integer that is divisible by the sum of its digits in a given number base. ... In mathematics, the Fibonacci numbers form a sequence defined recursively by: In other words: one starts with 0 and 1, and then produces the next Fibonacci number by adding the two previous Fibonacci numbers. ... The hertz (symbol Hz) is the SI unit of frequency. ... The blue box previously owned by Steve Wozniak, on display at the Computer History Museum. ... Long distance in telecommunications, refers to telephone calls made outside a certain area, usually characterized by an area code outside of a local call area. ... A telephone call is a connection over a telephone network between the calling party and the called party. ... Fall 2004 (21:3) 2600 Issue 2600: The Hacker Quarterly is a traditional (printed) magazine named for the fact that phreakers in the 1960s found that the transmission of a 2600 Hertz tone (which could be produced perfectly with a plastic toy whistle given away free with Capn Crunch... The Atari 2600, released in 1977, is the first successful video game console to use plug-in cartridges instead of having one or more games built in. ... A computer game is a game composed of a computer-controlled virtual universe that players interact with in order to achieve a defined goal or set of goals. ... Console may be: An organ term for the area of an organ including the keys, stops, and foot pedals manipulated by the organist. ... Amicable numbers are two numbers so related that the sum of the proper divisors of the one is equal to the other, unity being considered as a proper divisor but not the number itself. ... Cal Ripken, Jr. ... 8 {{{67}}} The eight queens puzzle is the problem of putting eight chess queens on an 8×8 chessboard such that none of them is able to capture any other using the standard chess queens moves. ... In mathematics, the Fibonacci numbers form a sequence defined recursively by: In words: you start with 0 and 1, and then produce the next Fibonacci number by adding the two previous Fibonacci numbers. ... A Markov number or Markoff number is an integer x, y or z that is part of a solution to the Markov Diophantine equation The first few Markov numbers are 1, 2, 5, 13, 29, 34, 89, 169, 194, 233, 433, 610, 985, 1325, ... (sequence A002559 in OEIS) appearing in... The magic constant of a magic square, an n-by-n matrix, is defined such that the sum of any row, column or main diagonal yields the same result, denoted M2(n). ... In mathematics, a magic square of order n is an arrangement of n² numbers in a square, such that the n numbers in all rows, all columns, and both diagonals sum to the same constant. ... 8 {{{67}}} The eight queens puzzle is the problem of putting eight chess queens on an 8×8 chessboard such that none of them is able to capture any other using the standard chess queens moves. ... A Smith number is a number which in a given base, the sum of its digits is equal to the sum of the digits in its factorization. ... A harmonic divisor number, or Ore number, is a number whose divisors, averaged in a harmonic mean, results in an integer. ... A chiliagonal number is a number that can be arranged to form a chiliagon. ...