cp's OEIS Frontend

A231011 Number of months after which a date can fall on the same day of the week, and the two months can have the same number of days, in the Julian calendar.

%I A231011 #4 Nov 02 2013 23:40:38
%S A231011 0,3,6,8,9,14,15,17,18,20,22,23,26,29,31,32,34,35,37,38,40,43,46,52,
%T A231011 54,55,57,60,63,64,68,69,72,75,77,78,80,81,86,89,92,94,95,98,101,103,
%U A231011 106,109,110,112,114,115,117,118,123,124,126,127,129,132,135,140,141,147,149,150
%N A231011 Number of months after which a date can fall on the same day of the week, and the two months can have the same number of days, in the Julian calendar.
%C A231011 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.
%C A231011 Assuming this fact, this sequence is periodic with a period of 336.
%C A231011 This is a subsequence of A231010.
%H A231011 Time And Date, <a href="http://www.timeanddate.com/calendar/repeating-month.html">Repeating Months</a>
%H A231011 Time And Date, <a href="http://www.timeanddate.com/calendar/julian-calendar.html">Julian Calendar</a>
%o A231011 (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]&&x[(q%336)+1]==x[((q+p)%336)+1],print1(p", ");break)))
%Y A231011 Cf. A230995-A231014.
%Y A231011 Cf. A231006 (Gregorian calendar).
%K A231011 nonn,easy
%O A231011 0,2
%A A231011 _Aswini Vaidyanathan_, Nov 02 2013