7 times triangular numbers: 7*n*(n+1)/2.

Terms

a(0) =0a(1) =7a(2) =21a(3) =42a(4) =70a(5) =105a(6) =147a(7) =196a(8) =252a(9) =315a(10) =385a(11) =462a(12) =546a(13) =637a(14) =735a(15) =840a(16) =952a(17) =1071a(18) =1197a(19) =1330a(20) =1470a(21) =1617a(22) =1771a(23) =1932a(24) =2100a(25) =2275a(26) =2457a(27) =2646a(28) =2842a(29) =3045