a(n) = 2^n * (n^4 - 4*n^3 + 18*n^2 - 52*n + 75) - 75.

Terms

a(0) =0a(1) =1a(2) =33a(3) =357a(4) =2405a(5) =12405a(6) =53877a(7) =207541a(8) =731829a(9) =2411445a(10) =7531445a(11) =22523829a(12) =64991157a(13) =181977013a(14) =496680885a(15) =1326120885a(16) =3473604533a(17) =8947236789a(18) =22706651061a(19) =56869519285a(20) =140755599285a(21) =344683708341a(22) =835954147253