Pentagonal pyramidal number
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A pentagonal pyramidal number is a number equal to the sum of the first few[citation needed] pentagonal numbers. The first few are 1, 6, 18, 40, 75, 126, 196, 288, 405, 550, 726, 936, 1183, 1470, 1800, 2176, 2601, 3078, 3610, 4200, 4851, 5566, 6348, 7200, 8125, and 9126.
example: The On-Line Encyclopedia of Integer Sequences:
A002411 Pentagonal pyramidal numbers: n^2*(n+1)/2.
FORMULA sum (n*j,j=0..n).
MAPLE : Epi:=(r, n)->stirling2(r, n): [seq (Epi(n+1, n) , n=0..41)];
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