G.f. A(x) satisfies 1 = Sum_{n=-oo..+oo} (A(x)^n - 2*x)^n.

Terms

a(0) =1a(1) =-2a(2) =5a(3) =-13a(4) =30a(5) =-74a(6) =202a(7) =-616a(8) =2126a(9) =-7828a(10) =29366a(11) =-110398a(12) =414214a(13) =-1556848a(14) =5892713a(15) =-22524354a(16) =86954484a(17) =-338421674a(18) =1324660464a(19) =-5204326208a(20) =20498580511a(21) =-80907096678a(22) =320002290542