OFFSET
0,5
FORMULA
G.f.: Sum_{k>=0} k! * x^k * ( (1-x)/(1-x^5) )^(k+1).
a(n) = Sum_{i, j, k, l>=0 and i+2*j+3*k+4*l<=n} (-1)^(i+j+k+l) * (n-j-2*k-3*l)!/(i!*j!*k!*l!).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=0, N, k!*x^k*((1-x)/(1-x^5))^(k+1)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 22 2024
STATUS
approved