Expansion of e.g.f.: 1/(1-2*tanh(x)).

Terms

a(0) =1a(1) =2a(2) =8a(3) =44a(4) =320a(5) =2912a(6) =31808a(7) =405344a(8) =5903360a(9) =96722432a(10) =1760811008a(11) =35260703744a(12) =770296217600