Sum(a(n)*x^n/n!) = exp(sinh(sinh(x))).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =9a(5) =33a(6) =153a(7) =731a(8) =4273a(9) =25857a(10) =177489a(11) =1311379a(12) =10342137a(13) =89060065a(14) =800697641a(15) =7778778091a(16) =78896218081a(17) =849264442881