Generalized Catalan numbers C(-3; n).

Terms

a(0) =1a(1) =1a(2) =-2a(3) =13a(4) =-98a(5) =826a(6) =-7448a(7) =70309a(8) =-686090a(9) =6865150a(10) =-70057772a(11) =726325810a(12) =-7628741204a(13) =81002393668a(14) =-868066319108