A231239 Number of months after which either it is not possible to have a date to fall on the same day of the week, or that it is possible to have a date falling on the same day of the week and the two months have the same number of days, in the Julian calendar.

0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 43, 44, 46, 47, 48, 50, 51, 52, 53, 54, 55, 56, 57, 59, 60, 62, 63, 64, 65, 67, 68, 69, 70, 72, 75, 76, 77, 78, 79, 80, 81, 82, 84, 85, 86, 88, 89

Offset

1,2

Comments

In the Julian calendar, a year is a leap year if and only if it is a multiple of 4 and all century years are leap years.

Assuming this fact, this sequence is periodic with a period of 336.

This is the complement of A231012.

Links

Table of n, a(n) for n=1..74.

Time And Date, Repeating Months

Time And Date, Julian 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(336, i, (m[((i-1)%12)+1]+((5*((i-1)\48)+(((i-1)\12)%4)-!((i-1)%48)-!((i-2)%48))))%7); x=vector(336, i, n[((i-1)%12)+1]+!((i-2)%48)); for(p=0, 336, j=0; for(q=0, 336, if(y[(q%336)+1]==y[((q+p)%336)+1], j=1; break)); for(q=0, 336, if(y[(q%336)+1]==y[((q+p)%336)+1]&&x[(q%336)+1]==x[((q+p)%336)+1], j=2; break)); if(j!=1, print1(p", ")))

Crossrefs

Cf. A230995-A231014, A231236-A231239.

Cf. A231238 (Gregorian calendar).

Sequence in context: A247801 A004775 A231238 * A335523 A328869 A004744

Adjacent sequences: A231236 A231237 A231238 * A231240 A231241 A231242

Keyword

nonn,easy

Author

Aswini Vaidyanathan, Nov 06 2013

Status

approved