G.f. A(x) satisfies: A(x) = x + x^2 * exp(3 * Sum_{k>=1} A(x^k) / k).

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =28a(5) =93a(6) =315a(7) =1109a(8) =3969a(9) =14505a(10) =53726a(11) =201588a(12) =764001a(13) =2921730a(14) =11257881a(15) =43669590a(16) =170383933a(17) =668236581a(18) =2632898016a(19) =10416893159a(20) =41368099791a(21) =164841324837a(22) =658883345595