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 A235865 #18 Aug 07 2018 12:48:01
%S A235865 4,8,12,15,16,20,24,32,36,40,48,56,60,64,72,80,96,100,105,108,112,120,
%T A235865 128,132,143,144,156,160,168,180,192,200,216,224,240,255,256,264,272,
%U A235865 280,288,300,312,320,324,336,360,380,384,385,392,396,399,400,432
%N A235865 G-Carmichael numbers: Composite number such that A235863(n) divides A201629(n).
%H A235865 Andrew Howroyd, <a href="/A235865/b235865.txt">Table of n, a(n) for n = 1..1038</a>
%H A235865 Jose María Grau, A. M. Oller-Marcen, Manuel Rodriguez and D. Sadornil, <a href="http://arxiv.org/abs/1401.4708">Fermat test with Gaussian base and Gaussian pseudoprimes</a>, arXiv:1401.4708 [math.NT], 2014.
%t A235865 FU[n_] := Which[Mod[n, 4] == 3, n + 1, Mod[n, 4] == 1, n - 1, True, n]; fa = FactorInteger; lam[1] = 1; lam[p_,s_] := Which[Mod[p, 4] == 3, p^(s - 1) (p + 1), Mod[p, 4] == 1, p^(s - 1) (p - 1), s ≥ 5, 2^(s -2), s > 1, 4, s == 1, 2]; lam[n_] := {aux = 1; Do[aux = LCM[aux, lam[fa[n][[i, 1]], fa[n][[i, 2]]]], {i, 1, Length[fa[n]]}]; aux}[[1]];Select[1+Range[1000], ! PrimeQ[#] && IntegerQ[FU[#]/lam[#]] &]
%o A235865 (PARI) ok(n)={my(f=factor(n), r=n-kronecker( -4, n)); for(i=1, #f~, my([p, e]=f[i, ]); my(t=if(p==2, 2^max(e-2, min(e, 2)), p^(e-1)*if(p%4==1, p-1, p+1))); if(r%t, return(0)) ); n>1 && !isprime(n)} \\ _Andrew Howroyd_, Aug 06 2018
%Y A235865 Cf. A235863, A201629.
%K A235865 nonn
%O A235865 1,1
%A A235865 _José María Grau Ribas_, Jan 16 2014
%E A235865 a(55) corrected by _Andrew Howroyd_, Aug 06 2018