a(n) = n^3 + 3*n + 3^n.

Terms

a(0) =1a(1) =7a(2) =23a(3) =63a(4) =157a(5) =383a(6) =963a(7) =2551a(8) =7097a(9) =20439a(10) =60079a(11) =178511a(12) =533205a(13) =1596559a(14) =4785755a(15) =14352327a(16) =43050865a(17) =129145127a(18) =387426375a(19) =1162268383a(20) =3486792461a(21) =10460362527a(22) =31381070323a(23) =94143191063a(24) =282429550377a(25) =847288625143