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 A139230 #11 Oct 20 2023 08:39:42 %S A139230 446,7164,33534576,8522776512,120292503552,2305842741852438528, %T A139230 2658455991569831740043006737112629248, %U A139230 191561942608236101977881394944640151127455097780436992 %N A139230 Second differences of perfect numbers A000396. %H A139230 Paolo Xausa, <a href="/A139230/b139230.txt">Table of n, a(n) for n = 1..13</a> %F A139230 a(n) = A139228(n+1) - A139228(n). - _Jinyuan Wang_, Mar 04 2020 %t A139230 Differences[PerfectNumber[Range[12]],2] (* _Paolo Xausa_, Oct 20 2023 *) %Y A139230 Cf. A000396, A139228, A139229, A139231, A139232, A139233, A139234, A139235, A139236, A139237. %K A139230 nonn %O A139230 1,1 %A A139230 _Omar E. Pol_, Apr 19 2008 %E A139230 a(5)-a(8) from _Jinyuan Wang_, Mar 04 2020