OFFSET
0,4
FORMULA
G.f.: Sum_{k>=0} k! * x^k * ( (1-x^2)/(1-x^6) )^(k+1).
a(n) = Sum_{i, j>=0 and 2*i+4*j<=n} (-1)^(i+j) * (n-i-3*j)!/(i!*j!).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=0, N, k!*x^k*((1-x^2)/(1-x^6))^(k+1)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 22 2024
STATUS
approved