A107417 a(n) = C(n+2,2)*C(n+5,5).

1, 18, 126, 560, 1890, 5292, 12936, 28512, 57915, 110110, 198198, 340704, 563108, 899640, 1395360, 2108544, 3113397, 4503114, 6393310, 8925840, 12273030, 16642340, 22281480, 29484000, 38595375, 50019606, 64226358, 81758656, 103241160, 129389040, 161017472, 199051776

Offset

0,2

Links

Table of n, a(n) for n=0..31.

Index entries for linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).

Formula

From Harvey P. Dale, Feb 18 2012: (Start)

a(0)=1, a(1)=18, a(2)=126, a(3)=560, a(4)=1890, a(5)=5292, a(6)=12936, a(7)=28512, a(n)=8*a(n-1)-28*a(n-2)+56*a(n-3)-70*a(n-4)+56*a(n-5)- 28*a(n-6)+ 8*a(n-7)-a(n-8).

G.f.: (10*x*(x+1)+1)/(x-1)^8. (End)

From Amiram Eldar, Sep 08 2022: (Start)

Sum_{n>=0} 1/a(n) = 25*Pi^2/3 - 5845/72.

Sum_{n>=0} (-1)^n/a(n) = 205/8 - 5*Pi^2/2. (End)

Example

If n=0 then C(0+2,2)*C(0+5,5) = C(2,2)*C(5,5) = 1*1 = 1.
If n=3 then C(3+2,2)*C(3+5,5) = C(5,2)*C(8,5) = 10*56 = 560.

Mathematica

Table[Binomial[n+2, 2]Binomial[n+5, 5], {n, 0, 40}] (* or *) LinearRecurrence[ {8, -28, 56, -70, 56, -28, 8, -1}, {1, 18, 126, 560, 1890, 5292, 12936, 28512}, 40] (* Harvey P. Dale, Feb 18 2012 *)

Prog

(PARI) for(n=0, 29, print1(binomial(n+2, 2)*binomial(n+5, 5), ", "))

Crossrefs

Cf. A062145.

Sequence in context: A292314 A002424 A101378 * A056125 A223212 A297027

Adjacent sequences: A107414 A107415 A107416 * A107418 A107419 A107420

Keyword

easy,nonn

Author

Zerinvary Lajos, May 26 2005

Extensions

More terms from Rick L. Shepherd, May 27 2005

Status

approved