a(n) = 7*n*(n+1)/2 - 5.

Terms

a(0) =2a(1) =16a(2) =37a(3) =65a(4) =100a(5) =142a(6) =191a(7) =247a(8) =310a(9) =380a(10) =457a(11) =541a(12) =632a(13) =730a(14) =835a(15) =947a(16) =1066a(17) =1192a(18) =1325a(19) =1465a(20) =1612a(21) =1766a(22) =1927a(23) =2095a(24) =2270a(25) =2452a(26) =2641a(27) =2837a(28) =3040a(29) =3250