OFFSET
0,2
FORMULA
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(n+k,k) * binomial(4*n+2,n-3*k).
D-finite with recurrence 81*n*(n-1)*(n+1)*a(n) -945*n^2*(n-1)*a(n-1) +441*(n-1)*(3*n^2+9*n-20)*a(n-2) +3*(1039*n^3 -12393*n^2 +37406*n-33232)*a(n-3) -448*(2*n-5) *(4*n-13)*(4*n-11)*a(n-4)=0. - R. J. Mathar, Jan 25 2024
MAPLE
A369114 := proc(n)
add(binomial(n+k, k) * binomial(4*n+2, n-3*k), k=0..floor(n/3)) ;
%/(n+1) ;
end proc;
seq(A369114(n), n=0..70) ; # R. J. Mathar, Jan 25 2024
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*((1-x)^3-x^3))/x)
(PARI) a(n) = sum(k=0, n\3, binomial(n+k, k)*binomial(4*n+2, n-3*k))/(n+1);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 13 2024
STATUS
approved