OFFSET
0,2
FORMULA
a(0) = 1; a(n) = Sum_{k=0..n-1} 3^(n-k) * (n-1+k)! / (k! * (n-1-k)!).
a(n) = 2*(2*n-3)*a(n-1) + 9*a(n-2).
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(3/2*(1-sqrt(1-4*x)))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 30 2024
STATUS
approved