login
G.f.: exp( Sum_{n>=1} 2*sigma(n*5^n)*x^n/n ).
2

%I #5 Mar 30 2012 18:37:27

%S 1,12,165,1820,19610,190006,1823415,16461130,146258245,1254022900,

%T 10573576571,86961051682,705575418795,5616255032890,44167926438195,

%U 342310177217866,2624766747036662,19886684916153110,149283882397744910

%N G.f.: exp( Sum_{n>=1} 2*sigma(n*5^n)*x^n/n ).

%e G.f.: A(x) = 1 + 12*x + 165*x^2 + 1820*x^3 + 19610*x^4 + 190006*x^5 +...

%e log(A(x)) = 12*x + 186*x^2/2 + 1248*x^3/3 + 10934*x^4/4 + 39062*x^5/5 + 468744*x^6/6 +...+ 2*sigma(n*5^n)*x^n/n +...

%o (PARI) {a(n)=polcoeff(exp(sum(m=1, n, 2*sigma(m*5^m)*x^m/m)+x*O(x^n)), n)}

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jul 15 2011