Odd integers k such that 5^((k-1)/2) + 1 == 0 (mod k*(k-1)/2).

Terms

a(0) =3a(1) =7a(2) =43a(3) =53a(4) =127a(5) =163a(6) =487a(7) =677a(8) =883a(9) =2647a(10) =8527a(11) =8803a(12) =14407a(13) =18523a(14) =26407a(15) =32887a(16) =35323a(17) =39367a(18) =71443a(19) =105967a(20) =184087a(21) =184843a(22) =230203a(23) =265483a(24) =319327a(25) =388963a(26) =425083a(27) =543607a(28) =554527a(29) =651043