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A224950 Leap years having 53 Fridays and Saturdays. 6
1588, 1616, 1644, 1672, 1712, 1740, 1768, 1796, 1808, 1836, 1864, 1892, 1904, 1932, 1960, 1988, 2016, 2044, 2072, 2112, 2140, 2168, 2196, 2208, 2236, 2264, 2292, 2304, 2332, 2360, 2388, 2416, 2444, 2472, 2512, 2540, 2568, 2596, 2608, 2636, 2664, 2692, 2704, 2732, 2760, 2788 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Gregorian calendar repeats after every 400 years because number of days in 400 years is 146097 which is a multiple of 7.
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.
15 occurrences in 400 years.
Months having Friday the 13th: May.
February 29th falls on Monday.
366 day leap year: 52 Sundays, 52 Mondays, 52 Tuesdays, 52 Wednesdays, 52 Thursdays, 53 Fridays, 53 Saturdays.
LINKS
Time and Date, The Gregorian calendar
Time and Date, 2016
Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).
MATHEMATICA
Needs["Calendar`"]; Select[Range[1583, 2800], DayOfWeek[{#, 1, 1}, Calendar -> Gregorian] == Friday && DaysBetween[{#, 1, 1}, {# + 1, 1, 1}, Calendar -> Gregorian] == 366 &, 50] (* T. D. Noe, Apr 22 2013 *)
ly53Q[y_]:=LeapYearQ[{y}]&&Count[DayRange[{y, 1, 1}, {y, 12, 31}], _?(DayName[ #]==Friday&)]==53&&Count[DayRange[{y, 1, 1}, {y, 12, 31}], _?(DayName[#] == Saturday&)] ==53; Select[Range[1570, 2800], ly53Q] (* Harvey P. Dale, Oct 14 2021, v9 or later *)
CROSSREFS
Sequence in context: A224941 A213116 A224942 * A233378 A083631 A224938
KEYWORD
nonn,changed
AUTHOR
Aswini Vaidyanathan, Apr 21 2013
STATUS
approved

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Last modified July 23 16:21 EDT 2024. Contains 374552 sequences. (Running on oeis4.)