A368839 a(n) = n! * (n+1)! * (n+2)! * Sum_{k=0..n} 1/(k! * (k+1)! * (k+2)!).

1, 7, 169, 10141, 1216921, 255553411, 85865946097, 43276436832889, 31159034519680081, 30847444174483280191, 40718626310317929852121, 69873162748505567626239637, 152602987442736159695707367209, 416606155718669715969281112480571

Offset: 0

Author

Seiichi Manyama, Jan 07 2024

Keywords

• nonn
• easy

Crossrefs

Cf. A000522, A228229.

Cf. A368840.

Programs

PARI

a(n) = n!*(n+1)!*(n+2)!*sum(k=0, n, 1/(k!*(k+1)!*(k+2)!));

Formula

a(n) = n*(n+1)*(n+2)*a(n-1) + 1.