A367058 G.f. satisfies A(x) = 1 + x*A(x)^3 + x^3*A(x)^2.

1, 1, 3, 13, 60, 301, 1595, 8774, 49631, 286870, 1686876, 10059301, 60689041, 369762262, 2271892435, 14060917955, 87579290486, 548558815484, 3453077437532, 21833406999880, 138603490377008, 883075187803622, 5644796991703781, 36191055027026410

Offset: 0

Author

Seiichi Manyama, Nov 04 2023

Keywords

• nonn

Crossrefs

Cf. A366676, A367057, A367059, A367060, A367061, A367062.

Programs

PARI

a(n) = sum(k=0, n\3, binomial(2*n-4*k+1, k)*binomial(3*n-7*k, n-3*k)/(2*n-4*k+1));

Formula

a(n) = Sum_{k=0..floor(n/3)} binomial(2*n-4*k+1,k) * binomial(3*n-7*k,n-3*k)/(2*n-4*k+1).