OFFSET
0,2
FORMULA
a(n) = GegenbauerPoly(n,-2*n-1,-1/2). - Emanuele Munarini, Oct 20 2016
G.f.: g/(1-g-3*g^2), where g = x times the g.f. of A143927. - Mark van Hoeij, Nov 16 2011
a(n) = Sum_{k=0..floor(n/2)} binomial(2*n+1,k)*binomial(2*n+1-k,n-2*k). - Emanuele Munarini, Oct 20 2016
MAPLE
seq(add(binomial(j, 2*j-2-3*n)*binomial(2*n+1, j), j=0...2*n+1), n=0..20); # Mark van Hoeij, May 12 2013
MATHEMATICA
Table[GegenbauerC[n, -2 n - 1, -1/2], {n, 0, 100}] (* Emanuele Munarini, Oct 20 2016 *)
PROG
(Maxima) makelist(ultraspherical(n, -2*n-1, -1/2), n, 0, 12); /* Emanuele Munarini, Oct 20 2016 */
(PARI) a(n)=sum(j=0, 2*n+1, binomial(j, 2*j-2-3*n)*binomial(2*n+1, j)); \\ Joerg Arndt, Oct 20 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Joerg Arndt, Oct 20 2016
STATUS
approved