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Product_{k>=1} (1+x^k)^a(k) = 1 + 5x.
9

%I #19 Jun 23 2018 14:17:37

%S 5,-10,40,-160,624,-2580,11160,-48910,217000,-976248,4438920,

%T -20346280,93900240,-435959820,2034504992,-9536767660,44878791360,

%U -211927516500,1003867701480,-4768372069968,22706531339280,-108372079190340,518301258916440,-2483526875798780

%N Product_{k>=1} (1+x^k)^a(k) = 1 + 5x.

%H Seiichi Manyama, <a href="/A038070/b038070.txt">Table of n, a(n) for n = 1..1000</a>

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

%F Dirichlet convolution of A038066 with characteristic function of powers of 2.

%F a(n) = 1/n*(-(-5)^n + Sum_{d<n and d|n} (-1)^(n/d)*d*a(d)). - _Seiichi Manyama_, Jun 23 2018

%Y Cf. A038063, A038064, A038065, A038066, A038067, A038068, A038069.

%K sign

%O 1,1

%A _Christian G. Bower_, Jan 04 1999