A026079 a(n) = Sum_{k = 1..n} T(k,k-1), where T is the array defined in A024996.

1, 3, 6, 12, 31, 83, 233, 661, 1893, 5445, 15720, 45510, 132069, 384049, 1118822, 3264644, 9539789, 27913085, 81769238, 239794424, 703906721, 2068153901, 6081507833, 17896695833, 52703944967, 155310270103, 457956633828, 1351132539606, 3988457429607

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A025179.

Programs

Mathematica

Join[{1, 3}, Table[Sum[ Binomial[n, 2*k]*Binomial[2*k + 1, k + 1], {k, 0, Floor[n/2]}] + 2, {n,2,50}]] (* G. C. Greubel, May 22 2017 *)

PARI

concat([1,3], for(n=2,50, print1(2 + sum(k=0,floor(n/2), binomial(n, 2*k)*binomial(2*k+1, k+1)), ", "))) \\ G. C. Greubel, May 22 2017

Formula

a(n) = A025179(n) + 2, n>2.