A138462 A bisection of A006318.

1, 6, 90, 1806, 41586, 1037718, 27297738, 745387038, 20927156706, 600318853926, 17518619320890, 518431875418926, 15521467648875090, 469286147871837366, 14308406109097843626, 439442782615614361662, 13582285614213903189954, 422158527806921249683014

Offset

0,2

Links

Colin Barker, Table of n, a(n) for n = 0..300

Formula

a(n) = A006318(2n).

a(n) = Sum_{i=0..2n} (C(2*n+1,i+1)*C(2*n+i,i))/(2*n+1). - Vladimir Kruchinin, Apr 02 2017

D-finite with recurrence +n*(2*n+1)*a(n) +(-70*n^2+73*n-15)*a(n-1) +(70*n^2-277*n+270)*a(n-2) -(2*n-5)*(n-3)*a(n-3)=0. - R. J. Mathar, Mar 25 2024

Prog

(Maxima)
a(n):=sum(binomial(2*n+1, i+1)*binomial(2*n+i, i), i, 0, 2*n)/(2*n+1); /* Vladimir Kruchinin, Apr 02 2017 */
(PARI) a(n) = sum(i=0, 2*n, binomial(2*n+1, i+1)*binomial(2*n+i, i))/(2*n+1) \\ Colin Barker, Dec 28 2017

Crossrefs

Sequence in context: A247150 A201073 A006480 * A379246 A002896 A266734

Adjacent sequences: A138459 A138460 A138461 * A138463 A138464 A138465

Keyword

nonn,easy

Author

N. J. A. Sloane, May 08 2008

Status

approved