a(n) = denominator(n!*[z^n]((cosh(x*z) + cos(x*z))*z/(1 - exp(-z)))(1)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =1a(4) =15a(5) =1a(6) =21a(7) =1a(8) =15a(9) =1a(10) =33a(11) =1a(12) =1365a(13) =1a(14) =3a(15) =1a(16) =255a(17) =1a(18) =399a(19) =1a(20) =1155a(21) =1a(22) =69a(23) =1a(24) =1365a(25) =1a(26) =21a(27) =1a(28) =435a(29) =1