A213552 Principal diagonal of the convolution array A213551.

1, 15, 81, 281, 756, 1722, 3486, 6462, 11187, 18337, 28743, 43407, 63518, 90468, 125868, 171564, 229653, 302499, 392749, 503349, 637560, 798974, 991530, 1219530, 1487655, 1800981, 2164995, 2585611, 3069186, 3622536, 4252952

Offset: 1

Author

Clark Kimberling, Jun 17 2012

Keywords

• nonn
• easy

Links

• Clark Kimberling, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

Crossrefs

Cf. A213551, A213500.

Programs

Mathematica

(See A213551.)

Formula

a(n) = n*(1 + n)*(2 + n)(-3 + 7*n + 16*n^2)/120.

a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6).

G.f.: x*(1 + 9*x + 6*x^2)/(1 - x)^6.