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A351514
Expansion of e.g.f. (exp(exp(exp(exp(x)-1)-1)-1)-1)^2 / 2.
3
1, 12, 136, 1650, 21904, 318521, 5051988, 86910426, 1612648066, 32107793135, 682724688430, 15439016490989, 369914992674530, 9359103270641290, 249292192469843244, 6971850327184526783, 204215496402215939638, 6251233458455082035922
OFFSET
2,2
FORMULA
a(n) = Sum_{k=1..n-1} binomial(n-1,k) * A000307(k) * A000307(n-k).
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace((exp(exp(exp(exp(x)-1)-1)-1)-1)^2/2))
(PARI) T(n, k) = if(k==0, n<=1, sum(j=0, n, stirling(n, j, 2)*T(j, k-1)));
a(n) = sum(k=1, n-1, binomial(n-1, k)*T(k, 4)*T(n-k, 4));
CROSSREFS
Column 2 of A039812.
Sequence in context: A194013 A189501 A373107 * A216081 A264503 A000467
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 12 2022
STATUS
approved