7 times hexagonal numbers: a(n) = 7*n*(2*n-1).

Terms

a(0) =0a(1) =7a(2) =42a(3) =105a(4) =196a(5) =315a(6) =462a(7) =637a(8) =840a(9) =1071a(10) =1330a(11) =1617a(12) =1932a(13) =2275a(14) =2646a(15) =3045a(16) =3472a(17) =3927a(18) =4410a(19) =4921a(20) =5460a(21) =6027a(22) =6622a(23) =7245a(24) =7896a(25) =8575a(26) =9282a(27) =10017a(28) =10780a(29) =11571