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 A127504 #6 Mar 30 2012 17:25:15 %S A127504 1,1,1,2,0,2,2,2,0,2,4,0,0,0,4,2,2,2,0,0,2,6,0,0,0,0,0,6,4,4,0,4,0,0, %T A127504 0,4,6,0,6,0,0,0,0,0,6,4,4,0,0,4,0,0,0,0,4 %N A127504 Triangle T(n,k) = phi(n) if k|n, =0 otherwise. %F A127504 T(n,k) = A000010(n)*A051731(n,k), 1<=k<=n. %e A127504 First few rows of the triangle are: %e A127504 1; %e A127504 1, 1; %e A127504 2, 0, 2; %e A127504 2, 2, 0, 2; %e A127504 4, 0, 0, 0, 4; %e A127504 2, 2, 2, 0, 0, 2; %e A127504 6, 0, 0, 0, 0, 0, 6; %e A127504 4, 4, 0, 4, 0, 0, 0, 4; %e A127504 ... %Y A127504 Cf. A051731, A062355 (row sums), A000010 (phi). %K A127504 nonn,tabl,easy %O A127504 1,4 %A A127504 _Gary W. Adamson_, Jan 17 2007