a(0) = 1, a(n) = (n + 4)*4^(n-1) for n >= 1.

Terms

a(0) =1a(1) =5a(2) =24a(3) =112a(4) =512a(5) =2304a(6) =10240a(7) =45056a(8) =196608a(9) =851968a(10) =3670016a(11) =15728640a(12) =67108864a(13) =285212672a(14) =1207959552a(15) =5100273664a(16) =21474836480a(17) =90194313216a(18) =377957122048