OFFSET
0,4
FORMULA
G.f.: A(x) = 2*(1 + x) / (1 + sqrt(1+4*x*(1 + x)^2)).
a(n) = Sum_{k=0..n} (-1)^k * binomial(2*k+1,k) * binomial(2*k+1,n-k) / (2*k+1).
D-finite with recurrence (n+1)*a(n) +(5*n-1)*a(n-1) +6*(2*n-3)*a(n-2) +6*(2*n-5)*a(n-3) +2*(2*n-7)*a(n-4)=0. - R. J. Mathar, Jul 25 2023
From Peter Bala, Aug 24 2024: (Start)
A(x) = (1 + x)*c(-x*(1+x)^2), where c(x) = (1 - sqrt(1 - 4*x))/(2*x) is the g.f. of the Catalan numbers A000108.
(1/x) * series_reversion(x/A(x)) = 1 - x^2 + 2*x^3 - 11*x^5 + 28*x^6 + ..., the g.f. of A364375. (End)
MAPLE
A364371 := proc(n)
add((-1)^k* binomial(2*k+1, k) * binomial(2*k+1, n-k)/(2*k+1), k=0..n) ;
end proc:
seq(A364371(n), n=0..70); # R. J. Mathar, Jul 25 2023
PROG
(PARI) a(n) = sum(k=0, n, (-1)^k*binomial(2*k+1, k)*binomial(2*k+1, n-k)/(2*k+1));
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Jul 20 2023
STATUS
approved