This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A284660 #16 May 09 2021 02:16:39 %S A284660 3083,4931,6563,9923,166667,865643,1306667,2266883,3367367,3906563, %T A284660 4128959,5493179,5591039,6040187,9122963,9402179,9871403,10174343, %U A284660 13081379,13756403,14924003,16550243,24165287,29492747,32140859,34633427,38425643,42249587,42258779,43014659,45067523,52678643 %N A284660 Terms of A161897 that are not in A005385. %C A284660 Primes p such that q = (p-1)/2 is composite, 3^q == 1 (mod p) and 3^(q-1) == 1 (mod p-1). %C A284660 All terms == 5 (mod 6). %H A284660 Robert Israel, <a href="/A284660/b284660.txt">Table of n, a(n) for n = 1..212</a> %e A284660 p = 3083 is in the sequence because it is prime, q = (3083-1)/2 = 23*67 is composite, 3^q == 1 (mod p) and 3^(q-1) == 1 mod (p-1). %p A284660 filter:= p -> isprime(p) and not isprime((p-1)/2) and %p A284660 3&^((p-3)/2) mod (p-1) = 1 and %p A284660 3 &^((p-1)/2) mod p = 1; %p A284660 select(filter, [seq(p, p=5..10^7, 6)]); # _Robert Israel_, Mar 31 2017 %Y A284660 Cf. A005385, A161897. %K A284660 nonn %O A284660 1,1 %A A284660 _Robert Israel_, Mar 31 2017