a(n) = n*(2*n + 1)*(4*n + 1).

Terms

a(0) =0a(1) =15a(2) =90a(3) =273a(4) =612a(5) =1155a(6) =1950a(7) =3045a(8) =4488a(9) =6327a(10) =8610a(11) =11385a(12) =14700a(13) =18603a(14) =23142a(15) =28365a(16) =34320a(17) =41055a(18) =48618a(19) =57057a(20) =66420a(21) =76755a(22) =88110a(23) =100533a(24) =114072a(25) =128775a(26) =144690a(27) =161865a(28) =180348a(29) =200187