Generalized Catalan numbers C(-4; n).

Terms

a(0) =1a(1) =1a(2) =-3a(3) =25a(4) =-251a(5) =2817a(6) =-33843a(7) =425769a(8) =-5537835a(9) =73865617a(10) =-1004862179a(11) =13888533561a(12) =-194475377243