G.f. satisfies: A(x) = exp( Sum_{n>=1} [A(x)^n + A(x)^-n]*x^n/n ).

Terms

a(0) =1a(1) =2a(2) =3a(3) =8a(4) =25a(5) =83a(6) =289a(7) =1041a(8) =3847a(9) =14504a(10) =55569a(11) =215727a(12) =846761a(13) =3354858a(14) =13398965a(15) =53888063a(16) =218053915a(17) =887107888a(18) =3626373205a(19) =14887942624a(20) =61358959587a(21) =253771944529