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 A068077 #12 Aug 04 2025 15:25:02 %S A068077 1,38184,458010,776112,65676408,1488668112,4414086384,28645019964, %T A068077 46696401675,65466785748,70619381496,176151711072 %N A068077 Numbers k such that sigma(k) + sigma(k+1) = 4k. %C A068077 a(13) > 10^13. - _Giovanni Resta_, Jul 11 2013 %t A068077 For[n=1, True, n++, If[DivisorSigma[1, n]+DivisorSigma[1, n+1]==4n, Print[n]]] %Y A068077 Cf. A000203 (sigma), A067806, A068078. %K A068077 more,nonn %O A068077 1,2 %A A068077 _Dean Hickerson_, Feb 16 2002 %E A068077 a(6)-a(8) from _Donovan Johnson_, Jan 31 2009 %E A068077 a(9)-a(12) from _Giovanni Resta_, Jul 11 2013