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 A231567 #6 Jan 12 2022 09:50:49
%S A231567 6,10,12,18,21,36,40,42,48,50,54,55,70,78,80,84,90,96,105,108,110,114,
%T A231567 126,136,144,147,150,156,160,162,165,168,170,171,186,189,190,200,210,
%U A231567 220,222,228,234,250,252,253,258,270,272,273,275,280,288,290,294
%N A231567 Numbers n such that A231566(n) <> n.
%t A231567 Su[n_] := Su[n] = Mod[Sum[GCD[i, n]*PowerMod[i, n, n], {i, 1, n}], n]; Select[Range[400], ! Su[2#] == # &]
%Y A231567 Cf. A231566.
%K A231567 nonn
%O A231567 1,1
%A A231567 _José María Grau Ribas_, Feb 01 2014