a(n) = 4*n^4 + 8*n^3 - 4*n - 1 = (2*n^2 - 1)*(2*n^2 + 4*n + 1).

Terms

a(0) =-1a(1) =7a(2) =119a(3) =527a(4) =1519a(5) =3479a(6) =6887a(7) =12319a(8) =20447a(9) =32039a(10) =47959a(11) =69167a(12) =96719a(13) =131767a(14) =175559a(15) =229439a(16) =294847a(17) =373319a(18) =466487a(19) =576079a(20) =703919a(21) =851927a(22) =1022119a(23) =1216607a(24) =1437599a(25) =1687399a(26) =1968407a(27) =2283119a(28) =2634127a(29) =3024119