Four times second pentagonal numbers: a(n) = 2*n*(3*n+1).

Terms

a(0) =0a(1) =8a(2) =28a(3) =60a(4) =104a(5) =160a(6) =228a(7) =308a(8) =400a(9) =504a(10) =620a(11) =748a(12) =888a(13) =1040a(14) =1204a(15) =1380a(16) =1568a(17) =1768a(18) =1980a(19) =2204a(20) =2440a(21) =2688a(22) =2948a(23) =3220a(24) =3504a(25) =3800a(26) =4108a(27) =4428a(28) =4760a(29) =5104