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

Terms

a(0) =2a(1) =3a(2) =7a(3) =17a(4) =31a(5) =53a(6) =79a(7) =109a(8) =157a(9) =199a(10) =263a(11) =331a(12) =401a(13) =479a(14) =577a(15) =661a(16) =773a(17) =887a(18) =1021a(19) =1153a(20) =1297a(21) =1459a(22) =1609a(23) =1787a(24) =1993a(25) =2161a(26) =2377a(27) =2609a(28) =2797a(29) =3041