OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..floor(n/2)} 3^(n-k) * Stirling2(n,2*k).
PROG
(PARI) my(N=30, x='x+O('x^N)); apply(round, Vec(serlaplace(cosh((exp(3*x)-1)/sqrt(3)))))
(PARI) a(n) = sum(k=0, n\2, 3^(n-k)*stirling(n, 2*k, 2));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 07 2022
STATUS
approved