E.g.f.: (1 + sinh(x)) / (1 - sinh(x)).

Terms

a(0) =1a(1) =2a(2) =4a(3) =14a(4) =64a(5) =362a(6) =2464a(7) =19574a(8) =177664a(9) =1814162a(10) =20583424a(11) =256891934a(12) =3497611264a(13) =51588733562a(14) =819450793984