4 times triangular numbers: a(n) = 2*n*(n+1).

Terms

a(0) =0a(1) =4a(2) =12a(3) =24a(4) =40a(5) =60a(6) =84a(7) =112a(8) =144a(9) =180a(10) =220a(11) =264a(12) =312a(13) =364a(14) =420a(15) =480a(16) =544a(17) =612a(18) =684a(19) =760a(20) =840a(21) =924a(22) =1012a(23) =1104a(24) =1200a(25) =1300a(26) =1404a(27) =1512a(28) =1624a(29) =1740