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%I #15 Mar 25 2024 09:04:34
%S 1,6,90,1806,41586,1037718,27297738,745387038,20927156706,
%T 600318853926,17518619320890,518431875418926,15521467648875090,
%U 469286147871837366,14308406109097843626,439442782615614361662,13582285614213903189954,422158527806921249683014
%N A bisection of A006318.
%H Colin Barker, <a href="/A138462/b138462.txt">Table of n, a(n) for n = 0..300</a>
%F a(n) = A006318(2n).
%F 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
%F 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
%o (Maxima)
%o 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 */
%o (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
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, May 08 2008
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