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 A053231 #6 Oct 27 2023 22:00:45 %S A053231 1,1,4,1,1,1,1,4,4,1,1,1,1,4,1,1,4,1,1,4,4,1,3,4,4,1,1,1,3,1,1,4,1,1, %T A053231 1,1,4,1,3,1,1,4,1,1,4,1,1,4,1,1,1,1,1,1,1,3,4,1,1,1,1,1,3,4,1,1,1,1, %U A053231 4,4,1,1,4,4,1,1,1,3,4,1,1,1,1,4,1,1,1,1,4,1,3,1,3,4,4,1,1,1,1,4,1,1,4,1,1 %N A053231 First differences between n for which sigma(n) < sigma(n+1), which are not 2. %F A053231 The expansion of A053230 excluding 2's. a(n) = A053230(A053232(n)). %p A053231 with(numtheory): f := [seq( `if`((sigma(i+1) > sigma(i)),i,print( )), i=1..5000)]; %p A053231 seq( `if`(f[i+1] - f[i] <> 2,f[i+1] - f[i],print( )), i=1..2000); %Y A053231 Cf. A000203, A053224, A053230, A053232, A053233, A053234, A053235, A053236, A053237. %K A053231 nonn %O A053231 1,3 %A A053231 _Asher Auel_, Jan 10 2000