login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A224943 Non-leap years beginning and ending on Friday. 0
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

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

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 15 12:31 EDT 2019. Contains 328026 sequences. (Running on oeis4.)