Triangular numbers equal to the difference between a prime number and its index.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =28a(5) =105a(6) =120a(7) =153a(8) =231a(9) =465a(10) =496a(11) =1081a(12) =1378a(13) =1485a(14) =1653a(15) =1711a(16) =2628a(17) =3003a(18) =3081a(19) =3160a(20) =4950a(21) =5050a(22) =5460a(23) =6670a(24) =6903a(25) =8001a(26) =8778a(27) =10296a(28) =11781a(29) =14028