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A365245
G.f. satisfies A(x) = 1 + x*A(x)/(1 - x^4*A(x)^3).
3
1, 1, 1, 1, 1, 2, 6, 16, 36, 72, 139, 283, 631, 1487, 3510, 8086, 18240, 41004, 93364, 216370, 507353, 1193113, 2799681, 6556243, 15368798, 36163695, 85483537, 202768647, 481870474, 1146143965, 2728316757, 6502751833, 15525113876, 37131739582
OFFSET
0,6
FORMULA
a(n) = Sum_{k=0..floor(n/4)} binomial(n-3*k-1,k) * binomial(n-k+1,n-4*k)/(n-k+1).
PROG
(PARI) a(n) = sum(k=0, n\4, binomial(n-3*k-1, k)*binomial(n-k+1, n-4*k)/(n-k+1));
CROSSREFS
Sequence in context: A038503 A352066 A351971 * A079990 A127902 A157136
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 28 2023
STATUS
approved