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

Terms

a(0) =-1a(1) =0a(2) =5a(3) =20a(4) =51a(5) =104a(6) =185a(7) =300a(8) =455a(9) =656a(10) =909a(11) =1220a(12) =1595a(13) =2040a(14) =2561a(15) =3164a(16) =3855a(17) =4640a(18) =5525a(19) =6516a(20) =7619a(21) =8840a(22) =10185a(23) =11660a(24) =13271a(25) =15024a(26) =16925a(27) =18980a(28) =21195a(29) =23576