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 A070193 #18 Apr 24 2025 02:15:04
%S A070193 253,1081,1771,2485,2783,3289,4301,4807,5405,5819,7337,7567,7843,9361,
%T A070193 10373,10879,11891,12397,12425,13409,13861,14053,14927,15433,17395,
%U A070193 17963,18145,18377,18469,19481,19987,20539,20999,22517,23023,24541
%N A070193 Numbers k such that gcd(3k,8^k+1) = 3 but k does not divide the numerator of B(2k) (the Bernoulli numbers).
%C A070193 Equivalently, numbers is in A070191 but not in A069040.
%H A070193 Amiram Eldar, <a href="/A070193/b070193.txt">Table of n, a(n) for n = 1..10000</a>
%t A070193 testb[n_] := Select[First/@FactorInteger[n], Mod[2n, #-1]==0&]=={}; test8[n_] := GCD[3n, PowerMod[8, n, 3n]+1]==3; Select[Range[25000], test8[ # ]&&!testb[ # ]&]
%o A070193 (PARI) isA070191(k) = gcd(3*k, Mod(8, 3*k)^k + 1) == 3;
%o A070193 isok(k) = if(!isA070191(k), 0, my(p = factor(k)[,1]); for(i = 1, #p, if(!((2*k) % (p[i]-1)), return(1))); 0); \\ _Amiram Eldar_, Apr 24 2025
%Y A070193 Cf. A027641, A069040, A070191, A070192.
%K A070193 nonn
%O A070193 1,1
%A A070193 _Benoit Cloitre_ and _Dean Hickerson_, Apr 26 2002