a(n) = prime(n*(n+1)/2 + n).

Terms

a(0) =3a(1) =11a(2) =23a(3) =43a(4) =71a(5) =103a(6) =149a(7) =193a(8) =251a(9) =313a(10) =389a(11) =463a(12) =569a(13) =653a(14) =761a(15) =881a(16) =1013a(17) =1129a(18) =1289a(19) =1451a(20) =1601a(21) =1777a(22) =1979a(23) =2143a(24) =2357a(25) =2591a(26) =2789a(27) =3023a(28) =3301a(29) =3539