a(n) = numerator(n!*[z^n](z*(exp(z)+2*exp(-(1/2)*z)*cos((1/2)*z* 3^(1/2)))/(1-exp(-z)))).

Terms

a(0) =3a(1) =3a(2) =1a(3) =3a(4) =59a(5) =5a(6) =43a(7) =7a(8) =139a(9) =9a(10) =-127a(11) =11a(12) =62099a(13) =13a(14) =-2513a(15) =15a(16) =278923a(17) =17a(18) =-16761307a(19) =19a(20) =13372769a(21) =21a(22) =-327211439a(23) =23a(24) =18102814403a(25) =25a(26) =-655076773a(27) =27a(29) =29a(31) =31