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 A053225 #6 Oct 27 2023 22:00:45 %S A053225 2,1,3,6,7,5,16,10,7,21,22,4,36,11,16,42,31,6,43,22,34,54,40,76,36,26, %T A053225 66,48,10,108,34,8,23,60,58,48,123,40,10,16,72,106,5,140,24,60,144,56, %U A053225 16,132,73,61,114,106,172,106,96,126,66,216,53,56,156,127,76,204,44,36 %N A053225 First differences of sigma(n) that are positive. %F A053225 a(n) = A053222(A053224(n)) %p A053225 with (numtheory): seq( `if`((sigma(i) < sigma(i+1)),(sigma(i+1)-sigma(i)),print( )), i=1..139); %Y A053225 Cf. A000203, A053222, A053227. %K A053225 nonn %O A053225 1,1 %A A053225 _Asher Auel_, Jan 06 2000