Heptagonal numbers (A000566) with prime indices (A000040).

Terms

a(0) =7a(1) =18a(2) =55a(3) =112a(4) =286a(5) =403a(6) =697a(7) =874a(8) =1288a(9) =2059a(10) =2356a(11) =3367a(12) =4141a(13) =4558a(14) =5452a(15) =6943a(16) =8614a(17) =9211a(18) =11122a(19) =12496a(20) =13213a(21) =15484a(22) =17098a(23) =19669a(24) =23377a(25) =25351a(26) =26368a(27) =28462a(28) =29539a(29) =31753