a(n) = n*(13*n - 9)/2.

Terms

a(0) =0a(1) =2a(2) =17a(3) =45a(4) =86a(5) =140a(6) =207a(7) =287a(8) =380a(9) =486a(10) =605a(11) =737a(12) =882a(13) =1040a(14) =1211a(15) =1395a(16) =1592a(17) =1802a(18) =2025a(19) =2261a(20) =2510a(21) =2772a(22) =3047a(23) =3335a(24) =3636a(25) =3950a(26) =4277a(27) =4617a(28) =4970a(29) =5336