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 A193879 #22 Jul 22 2025 12:31:43 %S A193879 0,2,4,6,8,11,12,15,16,28,29,32,33,36,38,40,42,44,47,48,51,52,64,65, %T A193879 68,69,72,74,76,78,80,83,84,87,88,100,101,104,105,108,110,112,114,116, %U A193879 119,120,123,124,136,137,140,141,144,146,148,150,152,155,156,159,160 %N A193879 Different leap years in the Gregorian and the revised Julian calendars. %C A193879 Terms divided by 100, e.g., 28 indicates year 2800, which is a Gregorian leap year, but not a revised Julian leap year. Values below 28 are "proleptic" (only based on the formula). %H A193879 M. Milankovitch, Das Ende des julianischen Kalenders und der neue Kalender der orientalischen Kirchen, Astronomische Nachrichten, <a href="http://articles.adsabs.harvard.edu/full/seri/AN.../0220/0000203.000.html">volume 220</a> (1924), pages 379-384. %H A193879 Claus Tøndering, Frequently Asked Questions about Calendars, <a href="http://www.tondering.dk/claus/cal/node3.html#SECTION00323000000000000000">Don't the Greeks do it differently?</a> %H A193879 Wikipedia, <a href="http://en.wikipedia.org/wiki/Revised_Julian_calendar">Revised Julian calendar</a> %F A193879 ( N // 9 = 2 | N // 9 = 6 ) <> ( N // 4 = 0 ) %e A193879 28 mod 9 is not 2 or 6, but 28 mod 4 is 0: 2800 is a Gregorian leap year. %e A193879 29 mod 9 is 2, but 29 mod 4 is not 0: 2900 is a revised Julian leap year. %Y A193879 A008586 enumerates "Gregorian leap centuries" (N // 4 = 0). %Y A193879 A193910 enumerates "revised Julian leap centuries". %K A193879 nonn,easy %O A193879 1,2 %A A193879 _Frank Ellermann_, Aug 07 2011