Triangular numbers n*(n+1)/2 with n prime and n+1 nonprime.

Terms

a(0) =6a(1) =15a(2) =28a(3) =66a(4) =91a(5) =153a(6) =190a(7) =276a(8) =435a(9) =496a(10) =703a(11) =861a(12) =946a(13) =1128a(14) =1431a(15) =1770a(16) =1891a(17) =2278a(18) =2556a(19) =2701a(20) =3160a(21) =3486a(22) =4005a(23) =4753a(24) =5151a(25) =5356a(26) =5778a(27) =5995a(28) =6441a(29) =8128