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 A097020 #5 Oct 21 2017 16:58:49
%S A097020 1,241,576,721,1249,2449,12481,23761,40897,65521,120049,126001,128016,
%T A097020 167041,186049,211248,211249,344449,374976,406801,417697,451249,
%U A097020 607201,647521,665856,708049,746641,766321,1039681,1068721,1092241,1146096
%N A097020 Initial terms of chains consisting of four consecutive integers, for none of which is the value of sigma-function divisible by six.
%C A097020 It is believed that in all of such quadruples remainder 3 always arises.
%e A097020 n=241: sigma-s for {241,242,243,244} are {242,399,364,434}
%e A097020 whose remainders modulo 6 are {2,3,4,2}.
%t A097020 SequencePosition[Table[If[Divisible[DivisorSigma[1,n],6],0,1],{n,12*10^5}],{1,1,1,1}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Oct 21 2017 *)
%Y A097020 Cf. A084301.
%K A097020 nonn
%O A097020 0,2
%A A097020 _Labos Elemer_, Aug 23 2004
%E A097020 Definition rephrased by _Harvey P. Dale_, Oct 21 2017