a(n) = Sum_{k=0..floor(n/2)} binomial(2*(n-2*k),k) * binomial(2*(n-2*k),n-2*k).

A361752

a(n) = Sum_{k=0..floor(n/2)} binomial(2*(n-2*k),k) * binomial(2*(n-2*k),n-2*k).

Terms

    a(0) =1a(1) =2a(2) =6a(3) =24a(4) =94a(5) =374a(6) =1520a(7) =6252a(8) =25942a(9) =108408a(10) =455586a(11) =1923444a(12) =8151856a(13) =34661252a(14) =147788484a(15) =631660788a(16) =2705471254a(17) =11609393084a(18) =49899207640a(19) =214792704256a(20) =925811868178

External references