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%I #2 Mar 30 2012 18:37:21
%S 1,3,12,47,157,531,1741,5459,16814,51286,152506,447622,1300571,
%T 3721897,10551143,29663448,82494469,227701487,624113377,1697228926,
%U 4586879327,12323255188,32904418872,87395198231,230972180615,607363842960
%N G.f.: exp( Sum_{n>=1} sigma(n*2^n)*x^n/n ).
%F The logarithmic derivative is A176311.
%o (PARI) {a(n)=polcoeff(exp(sum(k=1,n,sigma(k*2^k)*x^k/k)+x*O(x^n)),n)}
%Y Cf. A176311, A000203 (sigma).
%K nonn
%O 0,2
%A _Paul D. Hanna_, Apr 15 2010
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