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A138462

A bisection of A006318.

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

(list; graph; refs; listen; history; text; internal format)

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

URL: https://oeis.org/A138462

⇱ A138462 - OEIS