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 A174875 #16 Jun 29 2024 09:09:34 %S A174875 0,0,1,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0,1,1,0,1,3, %T A174875 1,3,0,1,1,1,1,1,1,1,1,0,0,0,0,0,2,0,2,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0, %U A174875 0,1,0,0,0,0,1,0,0,4,0,0,0,2,0,2,0,2,2,2,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 %N A174875 Triangle read by rows: T(n,k) = sigma(n) mod tau(k), where sigma(.) is the sum of divisors and tau(.) is the number of divisors. %e A174875 The triangle starts at row n=1 with columns k = 1..n: %e A174875 0; %e A174875 0,1; %e A174875 0,0,0; %e A174875 0,1,1,1; %e A174875 0,0,0,0,0; %e A174875 0,0,0,0,0,0; %e A174875 0,0,0,2,0,0,0; %e A174875 0,1,1,0,1,3,1,3; %e A174875 0,1,1,1,1,1,1,1,1; %e A174875 0,0,0,0,0,2,0,2,0,2; %e A174875 0,0,0,0,0,0,0,0,0,0,0; %t A174875 Array[Mod[DivisorSigma[1, #], DivisorSigma[0, Range[#]]] &, 15] (* _Paolo Xausa_, Jun 28 2024 *) %Y A174875 Cf. A000005, A000203, A054025 (right diagonal). %K A174875 nonn,tabl,easy %O A174875 1,25 %A A174875 _Juri-Stepan Gerasimov_, Dec 02 2010