cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

A051121 Dates at fortnightly intervals starting on Jan 01 of a leap year in the Julian calendar.

Original entry on oeis.org

1, 15, 29, 12, 26, 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, 29, 12, 26, 9, 23, 9, 23, 6, 20, 4, 18, 1, 15, 29, 13, 27, 10, 24, 7, 21, 5, 19, 2, 16, 30
Offset: 1

Views

Author

Karen Richardson (s1149414(AT)cedarville.edu)

Keywords

Comments

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

Links

Crossrefs

Cf. A001356.

Programs

  • Mathematica
    (* First program no longer functions in current Mathematica versions *)
Needs["Calendar`"]
Table[ DaysPlus[{4, 1, 1}, 14 n][[3]], {n, 0, 76}] (* Robert G. Wilson v, Apr 18 2010 *)
Table[DateValue[DayPlus[{2009, 1}, 14 n, CalendarType->"Julian"], "Day"], {n, 0, 77}] (* Michael De Vlieger, Mar 26 2017, Version 10, after Giovanni Resta at A001356; amended, Ray Chandler, Aug 07 2023 *)

Extensions

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

Views

Author

Jonathan Vos Post, Mar 02 2006

Keywords

Comments

"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."

Examples

			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).

References

  • 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.

Links

Crossrefs

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

Extensions

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

Views

Author

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

Keywords

Links

Crossrefs

Cf. A001356, A051121.

Programs

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

Extensions

Corrected by Harvey P. Dale, May 09 2021

A331542 The speed of light in furlongs per fortnight.

Original entry on oeis.org

1, 8, 0, 2, 6, 1, 7, 4, 9, 9, 7, 8, 5, 2, 5, 4, 1, 1, 5, 9, 6, 2, 7, 7, 7, 3, 8, 0, 1, 0, 0, 2, 1, 4, 7, 4, 5, 8, 8, 4, 0, 3, 7, 2, 2, 2, 6, 1, 9, 8, 9, 9, 7, 8, 5, 2, 5, 4, 1, 1, 5, 9, 6, 2, 7, 7, 7, 3, 8, 0, 1, 0, 0, 2, 1, 4, 7, 4, 5, 8, 8, 4, 0, 3, 7, 2, 2, 2, 6, 1, 9, 8
Offset: 13

Views

Author

Scott R. Shannon, Jan 19 2020

Keywords

Comments

Arguably the most well known FFF constant. Note that its precise value depends on the definition of the furlong being used. The value given here is using the international definition of the inch which equals 25.4 millimeters, thus one furlong equals 201.168 meters precisely.
From Jianing Song, Jan 25 2020: (Start)
Decimal expansion of 2518256647200000/1397.
Period 42: repeat [9, 9, 7, 8, 5, 2, 5, 4, 1, 1, 5, 9, 6, 2, 7, 7, 7, 3, 8, 0, 1, 0, 0, 2, 1, 4, 7, 4, 5, 8, 8, 4, 0, 3, 7, 2, 2, 2, 6, 1, 9, 8] since a(21). (End)

Links

Crossrefs

Cf. A003678, A001356.

Formula

1802617499785.2541159627773801002... furlongs/fortnight = (speed of light in meters/second) * (meter-to-furlong conversion) * (seconds/fortnight) = (299792458 meters/second) * (1/201.168 furlongs/meter) * (1209600 seconds/fortnight).
a(n) = 9 - a(n-21) for n >= 42. - Jianing Song, Jan 25 2020

Extensions

More terms from Jianing Song, Jan 25 2020
Showing 1-4 of 4 results.

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