OFFSET
0,1
LINKS
Paul D. Hanna, Table of n, a(n) for n = 0..400
FORMULA
Logarithmic derivative of the o.g.f. of A304319.
a(n) ~ sqrt(1-c) * 2^(2*n + 2) * n^(n + 3/2) / (sqrt(Pi) * c^(n + 3/2) * (2-c)^(n+1) * exp(n)), where c = -A226775 = -LambertW(-2*exp(-2)). - Vaclav Kotesovec, Aug 31 2020
EXAMPLE
O.g.f.: L(x) = 2 + 16*x + 260*x^2 + 6200*x^3 + 191832*x^4 + 7235152*x^5 + 320372320*x^6 + 16243028896*x^7 + 926219213216*x^8 + 58608051937536*x^9 + 4072302306624576*x^10 + ...
such that L(x) = F'(x)/F(x) where F(x) is the o.g.f. of A304319:
F(x) = 1 + 2*x + 10*x^2 + 104*x^3 + 1772*x^4 + 42408*x^5 + 1303504*x^6 + 48736000*x^7 + 2139552016*x^8 + 107629121888*x^9 + 6094743943584*x^10 + ... + A304319(n)*x^n + ...
which satisfies [x^n] exp( n*(n+1) * x ) / F(x) = 0 for n>0.
MATHEMATICA
m = 25;
F = 1 + Sum[c[k] x^k, {k, m}];
s[n_] := Solve[SeriesCoefficient[Exp[n*(n + 1)*x]/F, {x, 0, n}] == 0][[1]];
Do[F = F /. s[n], {n, m}];
CoefficientList[D[F, x]/F + O[x]^m, x] (* Jean-François Alcover, May 21 2018 *)
PROG
(PARI) {a(n) = my(A=[1], L); for(i=0, n, A=concat(A, 0); m=#A; A[m] = Vec( exp(x*m*(m-1) +x^2*O(x^m)) / Ser(A) )[m] ); L = Vec(Ser(A)'/Ser(A)); L[n+1]}
for(n=0, 25, print1( a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 11 2018
STATUS
approved