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

1,2

Links

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

Formula

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

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 *)

Prog

(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

Crossrefs

Cf. A025179.

Sequence in context: A219634 A252696 A288147 * A066710 A033648 A102972

Adjacent sequences: A026076 A026077 A026078 * A026080 A026081 A026082

Keyword

nonn

Author

Clark Kimberling

Status

approved