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A294840 Expansion of Product_{k>=1} (1 + x^(2*k-1))^(k*(5*k-3)/2)*(1 + x^(2*k))^(k*(5*k+3)/2). 3

%I #7 Nov 10 2017 11:31:27

%S 1,1,4,11,26,65,150,343,760,1670,3574,7561,15752,32396,65850,132386,

%T 263447,519316,1014744,1966234,3780464,7215020,13674227,25744768,

%U 48166429,89576421,165638008,304615115,557275053,1014398476,1837617957,3313527482,5948262037,10632231253,18926026208

%N Expansion of Product_{k>=1} (1 + x^(2*k-1))^(k*(5*k-3)/2)*(1 + x^(2*k))^(k*(5*k+3)/2).

%C Weigh transform of the generalized heptagonal numbers (A085787).

%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 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>

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

%F G.f.: Product_{k>=1} (1 + x^k)^A085787(k).

%F a(n) ~ 7^(1/8) * exp(Pi*sqrt(2) * 7^(1/4) * n^(3/4) / 3^(5/4) + 15*Zeta(3) * sqrt(3*n/7) / (4*Pi^2) - (7*Pi^6 + 4050*Zeta(3)^2)*n^(1/4) / (112*sqrt(2) * 3^(3/4) * 7^(1/4) * Pi^5) + 15*Zeta(3) * (7*Pi^6 + 5400*Zeta(3)^2) / (3136*Pi^8)) / (2^(7/3) * 3^(1/8) * n^(5/8)). - _Vaclav Kotesovec_, Nov 10 2017

%t nmax = 34; CoefficientList[Series[Product[(1 + x^(2 k - 1))^(k (5 k - 3)/2) (1 + x^(2 k))^(k (5 k + 3)/2), {k, 1, nmax}], {x, 0, nmax}], x]

%t a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d (5 d (d + 1)/8 + (-1)^d (2 d + 1)/16 - 1/16), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 34}]

%Y Cf. A028377, A085787, A294837, A294839, A294841.

%K nonn

%O 0,3

%A _Ilya Gutkovskiy_, Nov 09 2017

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