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 A015623 #11 Mar 30 2012 17:20:41 %S A015623 0,0,0,0,2,2,10,14,24,26,68,72,151,167,192,228,411,431,708,758,858, %T A015623 928,1419,1475,1874,2013,2353,2499,3515,3571,4856,5254,5747,6089,6795, %U A015623 6979,9129,9630,10437,10800,13768,13978,17500,18275,19210,20114,24734 %N A015623 Quadruples of different integers from [ 1,n ] with no common factors between pairs. %H A015623 Alois P. Heinz, <a href="/A015623/b015623.txt">Table of n, a(n) for n = 1..1000</a> %Y A015623 Partial sums of A185348, Column 4 of triangle A186974. %K A015623 nonn %O A015623 1,5 %A A015623 _Olivier Gérard_