Denominators in expansion of exp(2x)/(1-x).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =1a(5) =15a(6) =45a(7) =21a(8) =315a(9) =2835a(10) =4725a(11) =22275a(12) =93555a(13) =2027025a(14) =42567525a(15) =638512875a(16) =212837625a(17) =2170943775a(18) =13956067125a(19) =618718975875