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Expansion of Product_{k>=0} 1/(1 - x^(2*k*(k+1)+1)).
7

%I #8 May 08 2017 00:30:47

%S 1,1,1,1,1,2,2,2,2,2,3,3,3,4,4,5,5,5,6,6,7,7,7,8,8,10,11,11,12,12,14,

%T 15,15,16,16,18,19,19,21,22,24,26,26,28,29,31,33,33,35,36,39,42,43,45,

%U 47,50,53,54,56,58,61,65,66,69,72,76,81,83,86,89,93,98,100,103,107,112,118,121,125,130,136,142,146

%N Expansion of Product_{k>=0} 1/(1 - x^(2*k*(k+1)+1)).

%C Number of partitions of n into centered square numbers (A001844).

%H M. Bernstein and N. J. A. Sloane, <a href="http://arXiv.org/abs/math.CO/0205301">Some canonical sequences of integers</a>, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to arXiv version]

%H M. Bernstein and N. J. A. Sloane, <a href="/A003633/a003633_1.pdf">Some canonical sequences of integers</a>, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to Lin. Alg. Applic. version together with omitted figures]

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

%H <a href="/index/Ce#CENTRALCUBE">Index entries for sequences related to centered polygonal numbers</a>

%H <a href="/index/Par#partN">Index entries for related partition-counting sequences</a>

%F G.f.: Product_{k>=0} 1/(1 - x^(2*k*(k+1)+1)).

%e a(10) = 3 because we have [5, 5], [5, 1, 1, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1, 1, 1].

%t nmax = 82; CoefficientList[Series[Product[1/(1 - x^(2 k (k + 1) + 1)), {k, 0, nmax}], {x, 0, nmax}], x]

%Y Cf. A001156, A001844, A279220, A280950, A280952, A280953.

%K nonn

%O 0,6

%A _Ilya Gutkovskiy_, Jan 11 2017