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A230998 Number of years after which it is not possible to have a date falling on the same day of the week, in the Gregorian calendar. 1
1, 2, 3, 4, 8, 9, 10, 13, 14, 15, 16, 19, 20, 21, 24, 25, 26, 27, 30, 31, 32, 36, 37, 38, 41, 42, 43, 44, 47, 48, 49, 52, 53, 54, 55, 58, 59, 60, 64, 65, 66, 69, 70, 71, 72, 75, 76, 77, 80, 81, 82, 83, 86, 87, 88, 92, 93, 94, 97, 98, 99, 100, 103, 104, 105, 109, 110, 111 (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 A230995.

LINKS

Table of n, a(n) for n=1..68.

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

CROSSREFS

Cf. A230995-A231014.

Cf. A231003 (Julian calendar).

Sequence in context: A291621 A288860 A132115 * A184810 A246293 A047228

Adjacent sequences:  A230995 A230996 A230997 * A230999 A231000 A231001

KEYWORD

nonn,easy

AUTHOR

Aswini Vaidyanathan, Nov 02 2013

STATUS

approved

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Last modified October 17 11:47 EDT 2019. Contains 328108 sequences. (Running on oeis4.)