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A090651
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Perpetual calendar sequence: There are 14 basic year calendars, 7 for normal years and 7 for leap years. This sequence identifies the calendars for years 1901 through 2099, when it reinitializes because 2100 is not a leap year.
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2
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3, 4, 5, 13, 1, 2, 3, 11, 6, 7, 1, 9, 4, 5, 6, 14, 2, 3, 4, 12, 7, 1, 2, 10, 5, 6, 7, 8, 3, 4, 5, 13, 1, 2, 3, 11, 6, 7, 1, 9, 4, 5, 6, 14, 2, 3, 4, 12, 7, 1, 2, 10, 5, 6, 7, 8, 3, 4, 5, 13, 1, 2, 3, 11, 6, 7, 1, 9, 4, 5, 6, 14, 2, 3, 4, 12, 7, 1, 2, 10, 5, 6, 7, 8, 3, 4, 5, 13, 1, 2, 3, 11, 6, 7, 1, 9, 4
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1901,1
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COMMENTS
| 2000 was a leap year, so no reinitializing was needed.
Calendars are continuous so they roll from Dec 31 to Jan 01. The intercalation of the leap years causes the unusual sequence.
Note that a(n) = 1 for years starting on a Sunday, 2 for years starting on a Monday, so on to 7; 8 for leap years starting on a Sunday, 9 for leap years starting on Monday, so on to 14. - Alonso Delarte (alonso.delarte(AT)gmail.com), Nov 02 2004
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REFERENCES
| World Almanac 2003, Perpetual calendar on pages 647-648
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EXAMPLE
| a(2003) = 4 because 2003 is a year starting on a Wednesday.
a(2004) = 5 because 2004 is a leap year starting on a Thursday.
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CROSSREFS
| Sequence in context: A010752 A049929 A060738 * A062201 A049895 A051530
Adjacent sequences: A090648 A090649 A090650 * A090652 A090653 A090654
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KEYWORD
| nonn
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AUTHOR
| Brendan Sullivan (bsulliva(AT)austarnet.com.au), Dec 13 2003
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EXTENSIONS
| More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 23 2003
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