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%I #4 Nov 13 2013 15:19:20
%S 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,
%T 31,32,33,34,35,36,37,38,39,40,41,42,43,46,47,48,49,50,51,52,54,55,56,
%U 57,58,59,60,62,63,64,65,66,67,68,69,72,75,76,77,78,79,80,81,82,84,85,86,87
%N 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 Gregorian calendar.
%C 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.
%C Assuming this fact, this sequence is periodic with a period of 4800.
%C This is the complement of A231007.
%H Time And Date, <a href="http://www.timeanddate.com/calendar/repeating-month.html">Repeating Months</a>
%H Time And Date, <a href="http://www.timeanddate.com/calendar/gregorian-calendar.html">Gregorian Calendar</a>
%o (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],j=1;break));for(q=0,4800,if(y[(q%4800)+1]==y[((q+p)%4800)+1]&&x[(q%4800)+1]==x[((q+p)%4800)+1],j=2;break));if(j!=1,print1(p", ")))
%Y Cf. A230995-A231014, A231236-A231239.
%Y Cf. A231239 (Julian calendar).
%K nonn,easy
%O 1,2
%A _Aswini Vaidyanathan_, Nov 06 2013
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