A231008 Number of months after which it is not possible to have a date falling on the same day of the week, in the Gregorian calendar.

2, 4, 5, 7, 10, 12, 13, 16, 21, 24, 25, 30, 33, 36, 39, 42, 47, 48, 51, 56, 59, 62, 65, 79, 82, 85, 88, 93, 96, 97, 102, 105, 108, 111, 119, 120, 128, 134, 137, 139, 142, 148, 151, 154, 156, 157, 165, 168, 174, 180, 183, 188, 191, 192, 194, 197, 200, 211, 214, 220, 228, 229

Offset

1,1

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 4800.

This is the complement of A231005.

Links

Table of n, a(n) for n=1..62.

Time And Date, Repeating Months

Time And Date, Gregorian Calendar

Prog

(PARI) m=[0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5]; n=[31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]; y=vector(4800, i, (m[((i-1)%12)+1]+((5*((i-1)\48)+(((i-1)\12)%4)-((i-1)\1200)+((i-1)\4800)-!((i-1)%48)+!((i-1)%1200)-!((i-1)%4800)-!((i-2)%48)+!((i-2)%1200)-!((i-2)%4800))))%7); x=vector(4800, i, n[((i-1)%12)+1]+!((i-2)%48)-!((i-2)%1200)+!((i-2)%4800)); for(p=0, 4800, j=0; for(q=0, 4800, if(y[(q%4800)+1]==y[((q+p)%4800)+1], j=1; break)); if(j==0, print1(p", ")))

Crossrefs

Cf. A230995-A231014.

Cf. A231013 (Julian calendar).

Sequence in context: A285251 A325124 A231013 * A092311 A335365 A186386

Adjacent sequences: A231005 A231006 A231007 * A231009 A231010 A231011

Keyword

nonn,easy

Author

Aswini Vaidyanathan, Nov 02 2013

Status

approved