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 A224943 Non-leap years beginning and ending on Friday. 6
 1593, 1599, 1610, 1621, 1627, 1638, 1649, 1655, 1666, 1677, 1683, 1694, 1700, 1706, 1717, 1723, 1734, 1745, 1751, 1762, 1773, 1779, 1790, 1802, 1813, 1819, 1830, 1841, 1847, 1858, 1869, 1875, 1886, 1897, 1909, 1915, 1926, 1937, 1943, 1954, 1965, 1971, 1982, 1993, 1999 (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. 43 occurrences in 400 years. Months having Friday the 13th: August. 365 day ordinary year: 52 Sundays, 52 Mondays, 52 Tuesdays, 52 Wednesdays, 52 Thursdays, 53 Fridays, 52 Saturdays. LINKS Table of n, a(n) for n=1..45. Time and Date, The Gregorian calendar Time and Date, 2010 Wikipedia, Gregorian calendar Index entries for sequences related to calendars Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1). MATHEMATICA (* This first program no longer works in Mathematica version 10 because the relevant functions in that version have changed names. The second program, below, uses the functions now in Mathematica version 10 *) Select[Range[1583, 2600], DayOfWeek[{#, 1, 1}, Calendar -> Gregorian] == Friday && DaysBetween[{#, 1, 1}, {# + 1, 1, 1}, Calendar -> Gregorian] == 365 &, 50] (* T. D. Noe, Apr 22 2013 *) Select[Range[1590, 2000], DayName[{#, 1, 1}]==DayName[{#, 12, 31}]==Friday && !LeapYearQ[ {#, 1, 1}]&] (* Harvey P. Dale, Apr 26 2016 *) CROSSREFS Cf. A224938, A224939, A224940, A224941, A224942, A224944. Sequence in context: A224948 A238075 A250959 * A045273 A316336 A028893 Adjacent sequences: A224940 A224941 A224942 * A224944 A224945 A224946 KEYWORD nonn AUTHOR Aswini Vaidyanathan, Apr 21 2013 STATUS approved

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Last modified May 19 14:45 EDT 2024. Contains 372698 sequences. (Running on oeis4.)