a(n) = 26 + 2^(n+1)*(-13 +9*n -3*n^2 +n^3).

Terms

a(0) =0a(1) =2a(2) =34a(3) =250a(4) =1274a(5) =5274a(6) =19098a(7) =63002a(8) =194074a(9) =567322a(10) =1591322a(11) =4317210a(12) =11395098a(13) =29392922a(14) =74350618a(15) =184942618a(16) =453378074a(17) =1097334810a(18) =2626158618a(19) =6222250010a(20) =14610858010a(21) =34032582682a(22) =78693531674a(23) =180757725210a(24) =412685959194