G.f. A(x) satisfies A(x) = 1 + x*A(-x)^6.

Terms

a(0) =1a(1) =1a(2) =-6a(3) =-21a(4) =286a(5) =1281a(6) =-20592a(7) =-100226a(8) =1749462a(9) =8899086a(10) =-162993402a(11) =-852079872a(12) =16106878320a(13) =85783258295