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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;
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refs;
listen;
history;
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internal format)
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OFFSET
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1901,1
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COMMENTS
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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.
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 del Arte, Nov 02 2004
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REFERENCES
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World Almanac 2003, Perpetual calendar on pages 647-648.
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LINKS
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Table of n, a(n) for n=1901..1997.
Index entries for sequences related to calendars
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EXAMPLE
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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
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Sequence in context: A280308 A289121 A060738 * A242497 A062201 A352908
Adjacent sequences: A090648 A090649 A090650 * A090652 A090653 A090654
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KEYWORD
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nonn
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AUTHOR
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Brendan Sullivan (bsulliva(AT)austarnet.com.au), Dec 13 2003
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EXTENSIONS
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More terms from Ray Chandler, Dec 23 2003
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STATUS
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approved
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