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.

A163273 Fixed points of A036742.

Original entry on oeis.org

1659, 1669, 1679, 1689, 3620, 3621, 3622, 3623, 3624, 3630, 3631, 3632, 3633, 3634
Offset: 1

Views

Author

Claudio Meller, Jul 24 2009

Keywords

Formula

{n: A036742(n) = n}.

Extensions

Edited by R. J. Mathar, Jul 27 2009

A036741 Values increase, Roman numerals increase lexicographically.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 36, 37, 38
Offset: 1

Views

Author

David W. Wilson

Keywords

Comments

XXXVIII = 38 is the last entry in the Dictionary of Roman Numerals.

Crossrefs

Cf. A036742.

Programs

  • Python
    from roman import toRoman
last=100; A36741=[(last:=n) for n in range(1, 40) if toRoman(n)>toRoman(last)]
def A036741(n): return A36741[n-1] # M. F. Hasler, Aug 16 2025

A036743 Numbers <= 3999 sorted in Roman numeral reverse lexicographic order.

Original entry on oeis.org

38, 37, 36, 35, 39, 34, 33, 32, 31, 30, 28, 27, 26, 25, 29, 24, 23, 22, 21, 20, 18, 17, 16, 15, 48, 47, 46, 45, 49, 44, 43, 42, 41, 40, 19, 14, 13, 12, 11, 98, 97, 96, 95, 99, 94, 93, 92, 91, 90, 10, 8, 7, 6, 5, 1038, 1037, 1036, 1035, 1039, 1034, 1033, 1032
Offset: 1

Views

Author

David W. Wilson

Keywords

Links

Crossrefs

Cf. A036742.

Programs

A387014 Middle element of the list {1, 2, 3, ..., 2n-1} when elements are sorted lexicographically by their Roman numeral representations.

Original entry on oeis.org

1, 2, 3, 4, 9, 5, 6, 7, 8, 10, 11, 12, 13, 14, 19, 15, 16, 17, 18, 20, 18, 17, 16, 15, 48, 47, 46, 45, 49, 44, 43, 42, 41, 40, 19, 14, 13, 12, 11, 10, 8, 7, 6, 5, 88, 5, 6, 7, 8, 10, 8, 7, 6, 5, 88, 87, 86, 85, 89, 84, 83, 82, 81, 80, 78, 77, 76, 75, 79, 74, 73, 72, 71, 70
Offset: 1

Views

Author

José Hernández, Aug 13 2025

Keywords

Comments

Usual Roman numeral representations are taken as ending at 3999 so that here n <= 2000.
a(21) = 18 is the first repeated element, and 21 is also the least positive integer not in this sequence, which has 1690 distinct terms. More exhaustively, the positive integers not in this sequence are 21 .. 39, 90 .. 100, 200 .. 236, 239 .. 399, 450 .. 484, 489, 900 .. 999, 1005 .. 1008, 1010 .. 1049, 1090 .. 1099, 2001 .. 2099, 2101 .. 2199, 2205 .. 2208, 2210 .. 2249, 2251 .. 2299 and 2400 .. oo (where a .. b means all integers from a to b). - M. F. Hasler, Aug 18 2025

Examples

			For n = 5, the 2n-1 list elements sorted by Roman numerals are I, II, III, IV, IX, V, VI, VII, VIII and the middle element is IX = 9 = a(5).

Links

Crossrefs

Cf. A036742.

Programs

  • Mathematica
    Table[SortBy[Range[2*n-1], RomanNumeral][[n]], {n, 100}] (* Misha Lavrov via SeqFan *)
  • Python
    import roman
def A387014(n):
    return roman.fromRoman(sorted(roman.toRoman(k)for k in range(1,2*n))[n-1]) # M. F. Hasler, Aug 18 2025
Showing 1-4 of 4 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.