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 A071978 #3 Dec 05 2013 19:55:20
%S A071978 1,5,10,17,23,41,50,65,79,103,115,151,165,197,226,257,275,329,349,399,
%T A071978 436,483,507,577,608,665,706,771,801,913,945,1009,1063,1135,1186,1291,
%U A071978 1329,1409,1474,1573,1615,1763,1807,1905,1988,2083,2131,2275,2332,2457
%N A071978 Right diagonal of A071977.
%t A071978 a = {1}; k = 2; Do[i = 1; While[i < n + 1, If[ GCD[k, n] == 1, a = Append[a, k]; i++ ]; k++ ], {n, 2, 55}]; Table[ a[[n(n + 1)/2]], {n, 1, 55}]
%K A071978 nonn
%O A071978 1,2
%A A071978 _Amarnath Murthy_, Jun 18 2002
%E A071978 Edited by _Robert G. Wilson v_, Jun 28 2002