%I #4 Apr 19 2018 15:13:08

%S 1,1,1,1,1,6,31,106,281,631,1306,2806,6931,19306,55070,150816,391161,

%T 977501,2426071,6141865,16000186,42465571,112950916,297793651,

%U 776866355,2015237231,5233754306,13668689206,35908153534,94633042267,249398115466,656105299636,1723150461561

%N Number of ordered ways of writing n as a sum of n square pyramidal numbers.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SquarePyramidalNumber.html">Square Pyramidal Number</a>

%H <a href="/index/Ps#pyramidal_numbers">Index to sequences related to pyramidal numbers</a>

%F a(n) = [x^n] (Sum_{k>=0} x^(k*(k+1)*(2*k+1)/6))^n.

%F a(n) = A290430(n,n).

%t Table[SeriesCoefficient[Sum[x^(k (k + 1) (2 k + 1)/6), {k, 0, n}]^n, {x, 0, n}], {n, 0, 32}]

%Y Main diagonal of A290430.

%Y Cf. A000330, A066535, A279220, A287617, A303170.

%K nonn

%O 0,6

%A _Ilya Gutkovskiy_, Apr 19 2018