A051121 -id:A051121 - cp's OEIS frontend

A001356 Dates at fortnightly intervals from Jan 01 in the Julian calendar.

1, 15, 29, 12, 26, 12, 26, 9, 23, 7, 21, 4, 18, 2, 16, 30, 13, 27, 10, 24, 8, 22, 5, 19, 3, 17, 31, 14, 28, 11, 25, 11, 25, 8, 22, 6, 20, 3, 17, 1, 15, 29, 12, 26, 9, 23, 7, 21, 4, 18, 2, 16, 30, 13, 27, 10, 24, 10, 24, 7, 21, 5, 19, 2, 16, 30, 14, 28, 11, 25, 8, 22, 6, 20, 3, 17, 1, 15

Offset: 1

N. J. A. Sloane

Sequence assumes that the first year is the year after a leap year.

Periodic sequence with period 1461. - John Cerkan, Mar 26 2017

Archimedeans Problems Drive, Eureka, 13 (1950), 11.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

John Cerkan, Table of n, a(n) for n = 1..10000
John Cerkan, Python 2.7
Index entries for sequences related to calendars

Cf. A051121.

(* First program no longer functions in current Mathematica versions *)
(* first do *) Needs["Calendar`"]; (* then *) Table[Calendar`DaysPlus[{1, 1, 1}, 14 n][[3]], {n, 0, 77}] (* Robert G. Wilson v, Apr 18 2010 *)
Table[DateValue[DayPlus[{1,1,1},14 n,CalendarType->"Julian"],"Day"],{n,0,77}] (* recent Mathematica version, Giovanni Resta, Mar 22 2017; amended, Ray Chandler, Aug 07 2023 *)

More terms from Larry Reeves (larryr(AT)acm.org), Mar 17 2000
One more term from Robert G. Wilson v, Apr 18 2010
Name edited by Charles R Greathouse IV, Mar 27 2017

A115100 Mayan calendar periods in days.

Original entry on oeis.org

1, 20, 360, 7200, 144000, 1872000

Offset: 1

Jonathan Vos Post, Mar 02 2006

"Mayan primes" may be defined as these periods plus or minus 1, namely: 2, 19, 359, 143999, 1872001. Note also that 361 = 19^2; 144001 = 11 * 13 * 19 * 53.
From the Hermetic Systems" link: "The Mayas used three different calendrical systems (and some variations within the systems). The three systems are known as the tzolkin (the sacred calendar), the haab (the civil calendar) and the long count system. The tzolkin is a cycle of 260 days and the haab is a cycle of 365 days (these cycles are explained in Sections 2 and 3 of this chapter). The tzolkin cycle and the haab cycle were combined to produce a cycle of 18,980 days, known as the calendar round. 18,980 days is a little less than 52 solar years.
"Thus the Mayas could not simply use a tzolkin/haab date to identify a day within a period of several hundred years because there would be several days within this period with the same tzolkin/haab date. The Mayas overcame this problem by using a third dating system which enabled them to identify a day uniquely within a period of 1,872,000 days (approximately 5,125.36 solar years).
"To do this they used a vigesimal (i.e. based on 20) place-value number system, analogous to our decimal place-value number system. The Mayas used a pure vigesimal system for counting objects but modified this when counting days."

			1 kin = 1 day.
1 uinal = 20 kins = 20 days.
1 tun = 18 uinals = 360 days.
1 katun = 20 tuns = 7200 days.
1 baktun = 20 katuns = 144000 days.
13 baktuns = 1 great cycle or Maya era = 1872000 days (approximately 5125.37 solar years).

Bourgeois, Julia F., The True Calendar-Years of Aztecs and Mayas and the True Mayan Calendar System, Editorial Cultura, Mexico, 1942.
Bowditch, C. P., The Numeration, Calendar Systems and Astronomical Knowledge of the Mayas, Cambridge University Press, 1910.
Brunhouse, R. L., Sylvanus G. Morley and the World of the Ancient Mayas, University of Oklahoma Press, 1971.

Hermetic Systems: Maya and European Dates.
Index entries for sequences related to calendars

Cf. A008684, A008685, A011763, A011770, A011771.
Fortnight related: A001356, A051121.
Related to names of months: A031139.
A subsequence of A081244.

Edited by M. F. Hasler, Dec 23 2012

A115417 Dates of Sundays starting from Jan 01 2001.

Original entry on oeis.org

7, 14, 21, 28, 4, 11, 18, 25, 4, 11, 18, 25, 1, 8, 15, 22, 29, 6, 13, 20, 27, 3, 10, 17, 24, 1, 8, 15, 22, 29, 5, 12, 19, 26, 2, 9, 16, 23, 30, 7, 14, 21, 28, 4, 11, 18, 25, 2, 9, 16, 23, 30, 6, 13, 20, 27, 3, 10, 17, 24, 3, 10, 17, 24, 31, 7, 14, 21, 28, 5

Offset: 1

Jose A. Ruperez (josea(AT)ruperez.com), Mar 08 2006

nonn

Robert Israel, Table of n, a(n) for n = 1..10000

Cf. A001356, A051121.

# this requires Maple 2018 or later
with(Calendar):
d:= Date(2001,1,7):
R:=7:
for i from 2 to 100 do
  d:= AdjustDateField(d,"date",7);
  R:= R, DayOfMonth(d);
od:
R; # Robert Israel, Dec 30 2024

NestList[DatePlus[#,7]&,{2001,1,7},100][[All,3]] (* Harvey P. Dale, May 09 2021 *)

Corrected by Harvey P. Dale, May 09 2021

cp's OEIS Frontend

A001356 Dates at fortnightly intervals from Jan 01 in the Julian calendar.

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A115100 Mayan calendar periods in days.

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Author

Keywords

Comments

Examples

References

Links

Crossrefs

Extensions

A115417 Dates of Sundays starting from Jan 01 2001.

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Mathematica

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