a(n) = 4*n*(4*n - 1).

Terms

a(0) =0a(1) =12a(2) =56a(3) =132a(4) =240a(5) =380a(6) =552a(7) =756a(8) =992a(9) =1260a(10) =1560a(11) =1892a(12) =2256a(13) =2652a(14) =3080a(15) =3540a(16) =4032a(17) =4556a(18) =5112a(19) =5700a(20) =6320a(21) =6972a(22) =7656a(23) =8372a(24) =9120a(25) =9900a(26) =10712a(27) =11556a(28) =12432a(29) =13340