a(n) = Sum_{k=0..n} (-1)^k * binomial(4*k,n-k) * Catalan(k).

Terms

a(0) =1a(1) =-1a(2) =-2a(3) =5a(4) =6a(5) =-37a(6) =12a(7) =236a(8) =-454a(9) =-1038a(10) =5258a(11) =-688a(12) =-41780a(13) =79528a(14) =212032a(15) =-1067717a(16) =99414a(17) =9232114a(18) =-17976592a(19) =-49506598a(20) =255604634a(21) =-28864080a(22) =-2294742268a(23) =4618754686a(24) =12550067560a(25) =-67132100862a(26) =10660021188a(27) =612813797856