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

Terms

a(0) =1a(1) =16a(2) =49a(3) =100a(4) =169a(5) =256a(6) =361a(7) =484a(8) =625a(9) =784a(10) =961a(11) =1156a(12) =1369a(13) =1600a(14) =1849a(15) =2116a(16) =2401a(17) =2704a(18) =3025a(19) =3364a(20) =3721a(21) =4096a(22) =4489a(23) =4900a(24) =5329a(25) =5776a(26) =6241a(27) =6724a(28) =7225a(29) =7744