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 A261190 #9 Aug 18 2015 12:28:29 %S A261190 3,9,15,20,26,31,37,43,48,54,60,65,71,77,82,88,93,99,105,110,116,122, %T A261190 127,133,139,144,150,155,161,167,172,178,184,189,195,201,206,212,217, %U A261190 223,229,234,240,246,251,257,263,268,274,279,285,291,296,302,308,313 %N A261190 Leap years in Symmetry454 calendar, starting year AD 1. %C A261190 Year n is a leap year if and only if ((52 * n + 146) % 293) < 52. %H A261190 Felix Fröhlich, <a href="/A261190/b261190.txt">Table of n, a(n) for n = 1..10000</a> %H A261190 I. Bromberg, <a href="http://individual.utoronto.ca/kalendis/leap/52-293-sym454-leap-years.htm">52/293 Symmetry454 (start Monday) Leap Years</a> (Table of initial 780 terms) %H A261190 I. Bromberg, <a href="http://individual.utoronto.ca/kalendis/symmetry.htm#leap">The Symmetry454 Calendar - Leap Rule</a> %H A261190 Wikipedia, <a href="http://en.wikipedia.org/wiki/Symmetry454">Symmetry454</a> %o A261190 (PARI) is(n) = ((52*n+146)%293) < 52 %Y A261190 Cf. A057347, A057349, A189917. %K A261190 nonn %O A261190 1,1 %A A261190 _Felix Fröhlich_, Aug 11 2015