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A230996 Number of years after which an entire year can have the same calendar, in the Gregorian calendar. 3
0, 6, 11, 12, 17, 18, 22, 23, 28, 29, 34, 39, 40, 45, 46, 50, 51, 56, 57, 62, 67, 68, 73, 74, 78, 79, 84, 85, 90, 95, 96, 101, 102, 106, 107, 108, 112, 113, 114, 118, 119, 123, 124, 125, 129, 130, 134, 135, 136, 140, 141, 142, 146, 147, 151, 152, 153, 157, 158, 162 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
In the Gregorian calendar, a non-century year is a leap year if and only if it is a multiple of 4 and a century year is a leap year if and only if it is a multiple of 400.
Assuming this fact, this sequence is periodic with a period of 400.
This is a subsequence of A230995.
LINKS
Time And Date, Repeating Calendar
Time And Date, Gregorian Calendar
EXAMPLE
6 belongs to this sequence because year 2013 has the same calendar as year 2019.
11 belongs to this sequence because year 2002 has the same calendar as year 2013.
12 belongs to this sequence because year 2096 has the same calendar as year 2108.
PROG
(PARI) for(i=0, 400, for(y=0, 400, if(((5*(y\4)+(y%4)-(y\100)+(y\400))%7)==((5*((y+i)\4)+((y+i)%4)-((y+i)\100)+((y+i)\400))%7)&&((5*(y\4)+(y%4)-(y\100)+(y\400)-!(y%4)+!(y%100)-!(y%400))%7)==((5*((y+i)\4)+((y+i)%4)-((y+i)\100)+((y+i)\400)-!((y+i)%4)+!((y+i)%100)-!((y+i)%400))%7), print1(i", "); break)))
CROSSREFS
Cf. A231001 (Julian calendar).
Sequence in context: A276136 A152089 A212773 * A219553 A015870 A004471
KEYWORD
nonn,easy
AUTHOR
Aswini Vaidyanathan, Nov 02 2013
STATUS
approved

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Last modified June 16 12:34 EDT 2024. Contains 373429 sequences. (Running on oeis4.)