cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A300412 a(n) = [x^n] Product_{k>=1} ((1 + n*x^k)/(1 - n*x^k))^k.

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%I A300412 #10 Mar 06 2018 17:50:27
%S A300412 1,2,16,144,1376,15800,210816,3333372,61688448,1318588146,32004369200,
%T A300412 869282342632,26099925704928,857736429098848,30605729417479104,
%U A300412 1177841009504482200,48614265201514729984,2141639401723095243324,100282931820560447963568,4973060138191518242569120
%N A300412 a(n) = [x^n] Product_{k>=1} ((1 + n*x^k)/(1 - n*x^k))^k.
%F A300412 a(n) ~ 2 * n^n * (1 + 4/n + 14/n^2 + 44/n^3 + 124/n^4 + 328/n^5 + 824/n^6 + 1980/n^7 + 4590/n^8 + 10320/n^9 + 22584/n^10 + ...), for coefficients see A261451. - _Vaclav Kotesovec_, Mar 05 2018
%e A300412 The table of coefficients of x^k in expansion of Product_{k>=1} ((1 + n*x^k)/(1 - n*x^k))^k begins:
%e A300412 n = 0: (1),  0,   0,    0,     0,       0,  ...
%e A300412 n = 1:  1,  (2),  6,   16,    38,      88,  ...
%e A300412 n = 2:  1,   4, (16),  60,   192,     596,  ...
%e A300412 n = 3:  1,   6,  30, (144),  582,    2280,  ...
%e A300412 n = 4:  1,   8,  48,  280, (1376),   6568,  ...
%e A300412 n = 5:  1,  10,  70,  480,  2790,  (15800), ...
%t A300412 Table[SeriesCoefficient[Product[((1 + n x^k)/(1 - n x^k))^k, {k, 1, n}], {x, 0, n}], {n, 0, 19}]
%Y A300412 Cf. A156616, A261563, A266942, A270919, A270924, A292419, A298985, A298987.
%K A300412 nonn
%O A300412 0,2
%A A300412 _Ilya Gutkovskiy_, Mar 05 2018