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Pentatope number

A pentatope number is a number in the fifth cell of any row of Pascal's triangle starting with the 5-term row 1 4 6 4 1 either from left to right or from right to left. The first few numbers of this kind are

1, 5, 15, 35, 70, 126, 210, 330, 495, 715, 1001, 1365

Pentatope numbers belong in the class of figurate numbers, which can be represented as regular, discrete geometric patterns. The formula for the nth pentatopic number is:

{{n + 3} \choose 4} = n(n+1)(n+2)(n+3) / 24.

Many, but not all, pentatope numbers are also pentagonal numbers.

Last updated: 05-28-2005 04:05:55
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