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

Terms

a(0) =1a(1) =-1a(2) =-3a(3) =1a(4) =13a(5) =4a(6) =-49a(7) =-46a(8) =165a(9) =284a(10) =-476a(11) =-1417a(12) =1003a(13) =6220a(14) =-110a(15) =-24644a(16) =-14831a(17) =88184a(18) =113224a(19) =-278288a(20) =-619744a(21) =715647a(22) =2891977a(23) =-1036173a(24) =-12068353a(25) =-3381661a(26) =45588556a(27) =41600921a(28) =-154355594a(29) =-259984429