A081917 a(0)=1, a(n)= n^(n-2)(7n^2-3n+2)/6 (n>0).

1, 1, 4, 28, 272, 3375, 50976, 907578, 18612224, 432061533, 11200000000, 320680885976, 10051252125696, 342302635261067, 12586048547315712, 496928474121093750, 20968759865037029376, 941737183946729395897

Offset: 0

Author

Paul Barry, Mar 31 2003

Keywords

• easy
• nonn

Comments

Main diagonal of square array defined by T(n,k)=k^n(n^3-3n^2+2n+6k^3)/(6k^3), in which rows have g.f. (1-3kx+3k^2x^2-(k^3-1)x^3)/(1-kx)^4.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..100

Crossrefs

Cf. A050407, A081913, A081914, A081915, A081916.