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 A053239 #6 Oct 27 2023 22:00:45 %S A053239 4,1,1,4,4,1,1,1,1,4,4,1,1,4,4,1,1,4,1,1,1,1,3,1,1,1,1,1,4,3,1,4,1,1, %T A053239 4,4,1,1,3,1,4,1,1,4,1,1,4,1,1,4,4,4,3,1,1,1,4,4,3,1,1,1,4,4,1,1,1,1, %U A053239 4,1,1,1,1,4,3,1,4,4,1,1,4,4,1,1,3,1,3,1,1,1,1,1,4,4,1,1,4,1,1,4,4,3,1,3,1 %N A053239 First differences between n for which sigma(n) > sigma(n+1), which are not 2. %F A053239 The expansion of A053238 excluding 2's. a(n) = A053238(A053240(n)). %p A053239 with(numtheory): f := [seq( `if`((sigma(i) > sigma(i+1)),i,print( )), i=1..5000)]; %p A053239 seq( `if`(f[i+1] - f[i] <> 2,f[i+1] - f[i],print( )), i=1..2000); %Y A053239 Cf. A000203, A053226, A053238, A053240, A053241, A053242, A053243, A053244, A053245. %K A053239 nonn %O A053239 1,1 %A A053239 _Asher Auel_, Jan 10 2000