7 times heptagonal numbers: a(n) = 7*n*(5*n-3)/2.

Terms

a(0) =0a(1) =7a(2) =49a(3) =126a(4) =238a(5) =385a(6) =567a(7) =784a(8) =1036a(9) =1323a(10) =1645a(11) =2002a(12) =2394a(13) =2821a(14) =3283a(15) =3780a(16) =4312a(17) =4879a(18) =5481a(19) =6118a(20) =6790a(21) =7497a(22) =8239a(23) =9016a(24) =9828a(25) =10675a(26) =11557a(27) =12474a(28) =13426a(29) =14413