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 A093415 #17 Oct 21 2019 02:12:18 %S A093415 1,1,1,1,3,1,1,3,2,1,1,1,1,5,1,1,3,2,5,3,1,1,3,1,5,3,7,1,1,1,2,5,1,7, %T A093415 4,1,1,3,1,1,3,7,2,9,1,1,3,2,5,3,7,4,9,5,1,1,1,1,5,1,7,1,3,5,11,1,1,3, %U A093415 2,5,3,7,4,9,5,11,6,1,1,3,1,5,3,1,2,9,5,11,3,13,1,1,1,2,1,1,7,4,3,1,11,2 %N A093415 Triangle read by rows: a(n, k) is the denominator of (n + (n-1) + ... + (n-k+1))/(1 + 2 + ... + k), 0 < k <= n. %C A093415 A093412 gives the corresponding numerators. %C A093415 A109613(n+1) - 2 = 2*floor((n+1)/2) - 1 is the largest number in row n. [Corrected by _Petros Hadjicostas_, Oct 20 2019] %F A093415 a(n, k) = (k+1)/gcd(2n+2, k+1). %e A093415 Triangle a(n,k) (with rows n >= 1 and columns k >= 1) begins as follows: %e A093415 1; %e A093415 1, 1; %e A093415 1, 3, 1; %e A093415 1, 3, 2, 1; %e A093415 1, 1, 1, 5, 1; %e A093415 1, 3, 2, 5, 3, 1; %e A093415 1, 3, 1, 5, 3, 7, 1; %e A093415 1, 1, 2, 5, 1, 7, 4, 1; %e A093415 1, 3, 1, 1, 3, 7, 2, 9, 1; %e A093415 ... - _Petros Hadjicostas_, Oct 20 2019 %Y A093415 Cf. A109613, A093412, A093413, A093414, A093417. %K A093415 easy,nonn,tabl,frac %O A093415 1,5 %A A093415 _Amarnath Murthy_, Mar 30 2004 %E A093415 Edited and extended by _David Wasserman_, Feb 01 2006