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

A387353

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

Terms

    a(0) =1a(1) =0a(2) =2a(3) =12a(4) =50a(5) =220a(6) =1022a(7) =4760a(8) =22242a(9) =104700a(10) =495572a(11) =2355056a(12) =11230622a(13) =53718028a(14) =257609410a(15) =1238173072a(16) =5962959746a(17) =28767705252a(18) =139004456342a(19) =672608794340

External references