Triangular numbers (A000217) with prime indices.

Terms

a(0) =3a(1) =6a(2) =15a(3) =28a(4) =66a(5) =91a(6) =153a(7) =190a(8) =276a(9) =435a(10) =496a(11) =703a(12) =861a(13) =946a(14) =1128a(15) =1431a(16) =1770a(17) =1891a(18) =2278a(19) =2556a(20) =2701a(21) =3160a(22) =3486a(23) =4005a(24) =4753a(25) =5151a(26) =5356a(27) =5778a(28) =5995a(29) =6441