Smallest triangular number > 1 and == 1 (mod prime(n)).

Terms

a(0) =3a(1) =10a(2) =6a(3) =15a(4) =45a(5) =66a(6) =120a(7) =153a(8) =231a(9) =378a(10) =435a(11) =630a(12) =780a(13) =861a(14) =1035a(15) =1326a(16) =1653a(17) =1770a(18) =2145a(19) =2415a(20) =2556a(21) =3003a(22) =3321a(23) =3828a(24) =4560a(25) =4950a(26) =5151a(27) =5565a(28) =5778a(29) =6216