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 A224945 #24 Jul 21 2024 20:09:01
%S A224945 1584,1612,1640,1668,1696,1708,1736,1764,1792,1804,1832,1860,1888,
%T A224945 1928,1956,1984,2012,2040,2068,2096,2108,2136,2164,2192,2204,2232,
%U A224945 2260,2288,2328,2356,2384,2412,2440,2468,2496,2508,2536,2564,2592,2604,2632,2660,2688,2728,2756,2784
%N A224945 Leap years having 53 Sundays and Mondays.
%C A224945 Gregorian calendar repeats after every 400 years because number of days in 400 years is 146097 which is a multiple of 7.
%C A224945 Non-century years are leap years if and only if they are multiples of 4 while century years are leap years if and only if they are multiples of 400.
%C A224945 15 occurrences in 400 years.
%C A224945 Months having Friday the 13th: January, April and July.
%C A224945 February 29th falls on Wednesday.
%C A224945 366 day leap year: 53 Sundays, 53 Mondays, 52 Tuesdays, 52 Wednesdays, 52 Thursdays, 52 Fridays, 52 Saturdays.
%H A224945 Time and Date, <a href="http://www.timeanddate.com/calendar/gregorian-calendar.html">The Gregorian calendar</a>
%H A224945 Time and Date, <a href="http://www.timeanddate.com/calendar/?year=2012">2012</a>
%H A224945 Wikipedia, <a href="http://en.wikipedia.org/wiki/Gregorian_calendar">Gregorian calendar</a>
%H A224945 <a href="/index/Ca#calendar">Index entries for sequences related to calendars</a>
%H A224945 <a href="/index/Rec#order_16">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).
%t A224945 Needs["Calendar`"]; Select[Range[1583, 2800], DayOfWeek[{#, 1, 1}, Calendar -> Gregorian] == Sunday && DaysBetween[{#, 1, 1}, {# + 1, 1, 1}, Calendar -> Gregorian] == 366 &, 50] (* _T. D. Noe_, Apr 22 2013 *)
%t A224945 Select[Range[1583,3000],LeapYearQ[{#}]&&DayName[{#,1,1}]==Sunday&] (* _Harvey P. Dale_, Jul 04 2018, v9 or later *)
%Y A224945 Cf. A224946, A224947, A224948, A224949, A224950, A224951.
%K A224945 nonn
%O A224945 1,1
%A A224945 _Aswini Vaidyanathan_, Apr 21 2013