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A209397 L.g.f.: Sum_{n>=1} a(n)*x^n/n  =  Sum_{n>=1} x^n/n * exp( Sum_{k>=1} a(k)*x^(n*k)/k ). 4

%I

%S 1,3,7,19,46,129,337,939,2581,7238,20263,57337,162319,461961,1317217,

%T 3767035,10792400,30983565,89084845,256531814,739658815,2135234247,

%U 6170505666,17849457873,51679366171,149750711581,434260829464,1260198317509,3659410074933

%N L.g.f.: Sum_{n>=1} a(n)*x^n/n = Sum_{n>=1} x^n/n * exp( Sum_{k>=1} a(k)*x^(n*k)/k ).

%H Paul D. Hanna, <a href="/A209397/b209397.txt">Table of n, a(n) for n = 1..500</a>

%F a(n) = Sum_{d|n} d*A000081(d).

%F L.g.f.: Sum_{n>=1} -A000081(n) * log(1-x^n).

%F L.g.f.: log( G(x)/x ) = Sum_{n>=1} G(x^n)/n where G(x) is the g.f. of A000081, which is the number of rooted trees with n nodes.

%F a(n) ~ c * d^n / sqrt(n), where d = A051491 = 2.9557652856519949747148..., c = A187770 = 0.4399240125710253040409... . - _Vaclav Kotesovec_, Oct 30 2014

%e L.g.f.: L(x) = x + 3*x^2/2 + 7*x^3/3 + 19*x^4/4 + 46*x^5/5 + 129*x^6/6 +...

%e Let G(x) be the g.f. of A000081, then

%e exp(L(x)) = G(x)/x where G(x) = x*exp( Sum_{n>=1} G(x^n)/n ) begins:

%e G(x) = x + x^2 + 2*x^3 + 4*x^4 + 9*x^5 + 20*x^6 + 48*x^7 + 115*x^8 + 286*x^9 + 719*x^10 + 1842*x^11 + 4766*x^12 + 12486*x^13 + 32973*x^14 +...

%o (PARI) {a(n)=local(L=vector(n, i, 1)); for(i=1, n, L=Vec(deriv(sum(m=1, n, x^m/m*exp(sum(k=1, n\m, L[k]*x^(m*k)/k)+x*O(x^n)))))); L[n]}

%o for(n=1,30,print1(a(n),","))

%Y Cf. A000081, A203253.

%K nonn

%O 1,2

%A _Paul D. Hanna_, Mar 07 2012

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Last modified October 16 08:03 EDT 2018. Contains 316259 sequences. (Running on oeis4.)