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A231009
Number of months after which it is not possible to have the same calendar for the entire month with the same number of days, in the Gregorian calendar.
1
1, 2, 4, 5, 7, 10, 11, 12, 13, 16, 19, 21, 24, 25, 27, 28, 30, 33, 36, 39, 42, 44, 45, 47, 48, 51, 53, 56, 59, 61, 62, 65, 70, 71, 73, 74, 79, 82, 83, 85, 88, 91, 93, 96, 97, 99, 100, 102, 105, 108, 111, 116, 119, 120, 125, 128, 131, 133, 134, 137, 139, 142, 143, 145, 146, 148
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 4800.
This is the complement of A231006.
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]&&x[(q%4800)+1]==x[((q+p)%4800)+1], j=1; break)); if(j==0, print1(p", ")))
CROSSREFS
Cf. A231014 (Julian calendar).
Sequence in context: A296344 A060565 A231014 * A133254 A080725 A182337
KEYWORD
nonn,easy
AUTHOR
Aswini Vaidyanathan, Nov 02 2013
STATUS
approved