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User: Ehit Dinesh Agarwal

Ehit Dinesh Agarwal has authored 2 sequences.

A339738 Indices of distinct Gregorian calendar year types in a 400-year period, indexed in order of occurrence in the 3rd millennium CE.

1, 2, 3, 4, 5, 6, 1, 7, 8, 9, 5, 10, 2, 3, 8, 11, 6, 1, 2, 12, 9, 5, 6, 13, 3, 8, 9, 14, 1, 2, 3, 4, 5, 6, 1, 7, 8, 9, 5, 10, 2, 3, 8, 11, 6, 1, 2, 12, 9, 5, 6, 13, 3, 8, 9, 14, 1, 2, 3, 4, 5, 6, 1, 7, 8, 9, 5, 10, 2, 3, 8, 11, 6, 1, 2, 12, 9, 5, 6, 13, 3, 8, 9, 14

Offset: 1

Ehit Dinesh Agarwal, Jan 05 2021

nonn

The 3rd millennium CE began with the year 2001 CE.
There are 14 distinct Gregorian calendar year types, since a year may begin on any day of the week and it may or may not be a leap year.
This sequence has a period of 400 years because the sequence of leap years in the Gregorian calendar has a period of 400 years and the number of days in this 400-year period (146097) is a multiple of 7.
This sequence has an underlying cycle of 28 years that begins on the first year of a century and is disrupted by the last year of the century, except the century leap year.
All 14 calendar year types occur at least once in a 28-year cycle.
The shortest period that includes all 14 calendar year types is 25 years long (e.g., a(4) - a(28)). There are 79 such distinct periods.
The longest period that does not include all 14 calendar year types is 39 years long (e.g., a(65) - a(103)). There are 27 such distinct periods.
The 14 calendar year types occur with the following frequencies over a 400-year period: 43, 44, 43, 13, 43, 43, 14, 44, 43, 15, 15, 14, 13, 13.

			a(1) = 1 since 2001 CE is the first year of the 3rd millennium CE.
a(7) = 1 since 2007 CE, like 2001 CE, is not a leap year and begins on a Monday.
a(99) = 8; the 28-year cycle is disrupted after a(15).
a(100) = 9, instead of 11, since 2100 CE is not a leap year.
a(101) = 5; the 28-year cycle begins at a(5).
a(199) = 2; the 28-year cycle is disrupted after a(19).
a(200) = 3, instead of 12, since 2200 CE is not a leap year.
a(201) = 8; the 28-year cycle begins at a(9).
a(299) = 6; the 28-year cycle is disrupted after a(23).
a(300) = 1, instead of 13, since 2300 CE is not a leap year.
a(301) = 2; the 28-year cycle begins at a(13).
a(4)-a(28) is the shortest period that includes all 14 calendar year types.
a(65)-a(103) is the longest period that does not include all 14 calendar year types.

Ehit Dinesh Agarwal, Table of n, a(n) for n = 1..400
Index entries for sequences related to calendars

Cf. A127376.

A335232 Number of largest subsets of the set of points in an n X n square grid, such that no two points are at the same distance.

Original entry on oeis.org

1, 6, 40, 184, 280, 16, 8, 26800, 4376, 416, 16, 27488, 536, 587640, 10192, 128

Offset: 1

Ehit Dinesh Agarwal, May 27 2020

Ehit Dinesh Agarwal, C program
P. Erdős and R. K. Guy, Distinct distances between lattice points, Elemente der Mathematik 25 (1970), 121-123.
Matt Parker, MPMP: Unique Distancing Problem, Youtube video, May 2020.
Giovanni Resta, The essentially unique 7 x 7 configuration

Cf. A193838, A193839.
Size of largest subset in A271490.
Cf. A351699 (generalization to grid rectangles, counting congruent configurations only once).

a(14)-a(16) from Fausto A. C. Cariboni, Jul 03 2022

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User: Ehit Dinesh Agarwal

A339738 Indices of distinct Gregorian calendar year types in a 400-year period, indexed in order of occurrence in the 3rd millennium CE.

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