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A230999 Number of years after which it is not possible to have the same calendar for the entire year, in the Gregorian calendar. 1
1, 2, 3, 4, 5, 7, 8, 9, 10, 13, 14, 15, 16, 19, 20, 21, 24, 25, 26, 27, 30, 31, 32, 33, 35, 36, 37, 38, 41, 42, 43, 44, 47, 48, 49, 52, 53, 54, 55, 58, 59, 60, 61, 63, 64, 65, 66, 69, 70, 71, 72, 75, 76, 77, 80, 81, 82, 83, 86, 87, 88, 89, 91, 92, 93, 94, 97, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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 the complement of A230996.

LINKS

Table of n, a(n) for n=1..70.

Time And Date, Repeating Calendar

Time And Date, Gregorian Calendar

PROG

(PARI) for(i=0, 400, j=0; 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), j=1)); if(j==0, print1(i", ")))

CROSSREFS

Cf. A230995-A231014.

Cf. A231004 (Julian calendar).

Sequence in context: A165256 A175020 A050728 * A180590 A289342 A286302

Adjacent sequences:  A230996 A230997 A230998 * A231000 A231001 A231002

KEYWORD

nonn,easy

AUTHOR

Aswini Vaidyanathan, Nov 02 2013

STATUS

approved

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Last modified May 28 09:09 EDT 2022. Contains 354112 sequences. (Running on oeis4.)