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Product_{k>=1} 1/(1 - x^k)^a(k) = 1 + 3x.
7

%I #21 Jun 12 2018 08:10:30

%S 3,-6,8,-18,48,-124,312,-810,2184,-5928,16104,-44220,122640,-341796,

%T 956576,-2690010,7596480,-21524412,61171656,-174336264,498111952,

%U -1426419852,4093181688,-11767874940,33891544368,-97764131640

%N Product_{k>=1} 1/(1 - x^k)^a(k) = 1 + 3x.

%H Seiichi Manyama, <a href="/A038064/b038064.txt">Table of n, a(n) for n = 1..2000</a>

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

%F G.f.: Sum_{n>=1} moebius(n)*log(1 + 3*x^n)/n, where moebius(n)=A008683(n). - _Paul D. Hanna_, Oct 13 2010

%o (PARI) {a(n)=polcoeff(sum(k=1,n,moebius(k)/k*log(1+3*x^k+x*O(x^n))),n)} \\ _Paul D. Hanna_, Oct 13 2010

%Y Cf. A038063, A038064, A038065, A038066, A038067, A038068, A038069, A038070.

%K sign

%O 1,1

%A _Christian G. Bower_, Jan 04 1999