a(n) = Sum_{i=0..(n+1)/2} binomial(2*i+1,i)*binomial(2*n-2*i,n)/(2*i+1).

A270490

a(n) = Sum_{i=0..(n+1)/2} binomial(2*i+1,i)*binomial(2*n-2*i,n)/(2*i+1).

Terms

    a(0) =1a(1) =2a(2) =7a(3) =24a(4) =87a(5) =320a(6) =1195a(7) =4504a(8) =17102a(9) =65304a(10) =250501a(11) =964480a(12) =3724996a(13) =14424504a(14) =55983091a(15) =217702880a(16) =848042197a(17) =3308490496a(18) =12924954514a(19) =50553798696a(20) =197948515868a(21) =775853655760

External references