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%I #4 Oct 07 2020 08:43:49
%S 1,2,5,14,61,370,3454,40880,614346,10848514,222870183,5175100204,
%T 134514302384,3859406052466,121274242936381,4139268759072626,
%U 152532132931199062,6034430112251517608,255114747410233804986
%N G.f.: A(x) = exp( Sum_{n>=1} 2*sigma(n,n-1)*x^n/n ).
%e G.f.: A(x) = 1 + 2*x + 5*x^2 + 14*x^3 + 61*x^4 + 370*x^5 +...
%o (PARI) a(n)=polcoeff(exp(sum(m=1,n,2*sigma(m,m-1)*x^m/m)+x*O(x^n)),n)
%Y Cf. A023881, A294645.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Mar 20 2009
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