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 A286854 #23 Feb 09 2021 01:55:10
%S A286854 55,253,275,385,605,715,935,1045,1081,1265,1375,1595,1705,1711,1771,
%T A286854 1925,2035,2255,2365,2485,2585,2695,2783,2915,3025,3245,3289,3355,
%U A286854 3403,3575,3685,3905,4015,4235,4301,4345,4565,4675,4807,4895,5005,5225,5335,5405,5555
%N A286854 Numbers k such that k == 1 or -1 (mod 6) but k does not divide the numerator of Bernoulli(2*k).
%p A286854 isa := n -> abs(mods(n, 6)) = 1 and modp(numer(bernoulli(2*n)), n) <> 0:
%p A286854 select(isa, [$1..2255]); # _Peter Luschny_, Aug 02 2017
%t A286854 Select[Range@9999,0 != Mod[Numerator@BernoulliB[2 #], #] && MemberQ[{1, 5}, Mod[#, 6]] &]
%o A286854 (PARI) isok(n) = (((n % 6) == 1) || ((n % 6) == 5)) && (numerator(bernfrac(2*n)) % n); \\ _Michel Marcus_, Aug 02 2017
%Y A286854 Cf. A000367, A286853 (1st differences).
%K A286854 nonn
%O A286854 1,1
%A A286854 _Bill Gosper_, Aug 01 2017