cp's OEIS Frontend

A231012 Number of months after which a date can fall on the same day of the week, but it is not possible that the two months have the same number of days, in the Julian calendar.

%I A231012 #4 Nov 02 2013 23:40:44
%S A231012 1,11,19,27,28,41,45,49,58,61,66,71,73,74,83,87,91,100,104,113,121,
%T A231012 130,131,133,138,143,146,159,160,176,177,190,193,198,203,205,206,215,
%U A231012 223,232,236,245,249,253,262,263,265,270,275,278,287,291,295,308,309,317,325,335
%N A231012 Number of months after which a date can fall on the same day of the week, but it is not possible that the two months have the same number of days, in the Julian calendar.
%C A231012 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 A231012 Assuming this fact, this sequence is periodic with a period of 336.
%C A231012 These are the terms of A231010 not in A231011.
%H A231012 Time And Date, <a href="http://www.timeanddate.com/calendar/repeating-month.html">Repeating Months</a>
%H A231012 Time And Date, <a href="http://www.timeanddate.com/calendar/julian-calendar.html">Julian Calendar</a>
%o A231012 (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", ")))
%Y A231012 Cf. A230995-A231014.
%Y A231012 Cf. A231007 (Gregorian calendar).
%K A231012 nonn,easy
%O A231012 1,2
%A A231012 _Aswini Vaidyanathan_, Nov 02 2013