a(0) = 0 and a(n) = (5*(-4)^n + 16*(-1)^n + 9*4^n)/240 for n >= 1.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =15a(5) =17a(6) =239a(7) =273a(8) =3823a(9) =4369a(10) =61167a(11) =69905a(12) =978671a(13) =1118481a(14) =15658735a(15) =17895697a(16) =250539759a(17) =286331153a(18) =4008636143a(19) =4581298449a(20) =64138178287a(21) =73300775185