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Encyclopedia > Octahedral number

An octahedral number is a figurate number that represents an octahedron, or two pyramids placed together, one upside-down underneath the other. The octahedral number for n can be obtained by adding the n-1 and n square pyramidal numbers together, or by using the following formula:


{1 \over 3}n(2n^2 + 1)


The first few octahedral numbers are


1, 6, 19, 44, 85, 146, 231, 344, 489, 670, 891


  Results from FactBites:
 
85 (number) - Wikipedia, the free encyclopedia (242 words)
Eighty-five is an octahedral number, a centered triangular number, a centered square number, a decagonal number, and a Smith number.
The Saros number of the solar eclipse series which began on -170 March 14 and ended on 1110 April 20.
Further, the Saros number of the lunar eclipse series which began on -103 August 2 and ended on 1267 November 3.
  More results at FactBites »

 

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