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Expansion of Product_{k>=1} (1 + x^(k*(k+1)*(2*k+1)/6)).
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%I #4 Jan 15 2018 21:06:41

%S 1,1,0,0,0,1,1,0,0,0,0,0,0,0,1,1,0,0,0,1,1,0,0,0,0,0,0,0,0,0,1,1,0,0,

%T 0,1,1,0,0,0,0,0,0,0,1,1,0,0,0,1,1,0,0,0,0,1,1,0,0,0,1,1,0,0,0,0,0,0,

%U 0,1,1,0,0,0,1,1,0,0,0,0,0,0,0,0,0,1,1,0,0,0,1,2,1,0,0,0,1,1,0,1,1,0,0,0,1

%N Expansion of Product_{k>=1} (1 + x^(k*(k+1)*(2*k+1)/6)).

%C Number of partitions of n into distinct 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/Par#part">Index entries for related partition-counting sequences</a>

%F G.f.: Product_{k>=1} (1 + x^A000330(k)).

%e a(91) = 2 because we have [91] and [55, 30, 5, 1].

%t nmax = 104; CoefficientList[Series[Product[1 + x^(k (k + 1) (2 k + 1)/6), {k, 1, nmax}], {x, 0, nmax}], x]

%Y Cf. A000330, A033461, A279220, A279278, A289895.

%K nonn

%O 0,92

%A _Ilya Gutkovskiy_, Jan 15 2018