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 A139229 #14 Oct 20 2023 08:40:18 %S A139229 11,234,3816,16771104,4278159360,64424411136,1152921435350630400, %T A139229 1329227995784915871174424803906945024, %U A139229 95780971304118052318168693257235946738152352797163520 %N A139229 First differences of perfect numbers A000396, divided by 2. %H A139229 Paolo Xausa, <a href="/A139229/b139229.txt">Table of n, a(n) for n = 1..14</a> %F A139229 a(n) = A139228(n)/2. %t A139229 Differences[Select[Range[10000], DivisorSigma[1, #] == 2# &]]/2 (* _Alonso del Arte_, Mar 05 2020 *) %t A139229 Differences[PerfectNumber[Range[12]]]/2 (* _Paolo Xausa_, Oct 20 2023 *) %Y A139229 Cf. A000396, A139228, A139230, A139231, A139232, A139233, A139234, A139235, A139236, A139237. %K A139229 nonn %O A139229 1,1 %A A139229 _Omar E. Pol_, Apr 19 2008 %E A139229 a(6)-a(9) from A139228(n)/2 by _Jinyuan Wang_, Mar 04 2020