A231010 Number of months after which a date can fall on the same day of the week, in the Julian calendar.

0, 1, 3, 6, 8, 9, 11, 14, 15, 17, 18, 19, 20, 22, 23, 26, 27, 28, 29, 31, 32, 34, 35, 37, 38, 40, 41, 43, 45, 46, 49, 52, 54, 55, 57, 58, 60, 61, 63, 64, 66, 68, 69, 71, 72, 73, 74, 75, 77, 78, 80, 81, 83, 86, 87, 89, 91, 92, 94, 95, 98, 100, 101, 103, 104, 106, 109, 110, 112

Offset: 0

Author

Aswini Vaidyanathan, Nov 02 2013

Keywords

• nonn
• easy

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.

Links

• Time And Date, Repeating Months
• Time And Date, Julian Calendar

Crossrefs

Cf. A230995-A231014.

Cf. A231005 (Gregorian calendar).

Programs

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,for(q=0,336,if(y[(q%336)+1]==y[((q+p)%336)+1],print1(p", ");break)))