Triangular numbers T from A000217 such that (4*T+1)/13 is prime.

Terms

a(0) =55a(1) =120a(2) =1485a(3) =1953a(4) =2278a(5) =2850a(6) =3240a(7) =6555a(8) =9870a(9) =10585a(10) =16110a(11) =17020a(12) =18528a(13) =34453a(14) =36585a(15) =37950a(16) =47895a(17) =49455a(18) =52003a(19) =56280a(20) =57970a(21) =70125a(22) =72010a(23) =80200a(24) =96580a(25) =110685a(26) =127260a(27) =129795a(28) =133903a(29) =165025