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 1-5 of 5 results.

A007320 Number of steps needed for juggler sequence (A094683) started at n to reach 1.

Original entry on oeis.org

0, 1, 6, 2, 5, 2, 4, 2, 7, 7, 4, 7, 4, 7, 6, 3, 4, 3, 9, 3, 9, 3, 9, 3, 11, 6, 6, 6, 9, 6, 6, 6, 8, 6, 8, 3, 17, 3, 14, 3, 5, 3, 6, 3, 6, 3, 6, 3, 11, 5, 11, 5, 11, 5, 11, 5, 5, 5, 11, 5, 11, 5, 5, 3, 5, 3, 11, 3, 14, 3, 5, 3, 8, 3, 8, 3, 19, 3, 8, 3, 10, 8, 8, 8, 11, 8, 10, 8, 11, 8, 11, 8, 11, 8, 8, 8, 11
Offset: 1

Views

Author

Keywords

Comments

It is not known if every starting value eventually reaches 1.

Examples

			The trajectory of 1 is 3, 5, 11, 36, 6, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ... so a(3) = 6.
		

References

  • C. Pickover, Computers and the Imagination, St. Martin's Press, NY, 1991, p. 232.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Maple
    A007320 := proc(n)
        local a,ntrack;
        a := 0 ;
        ntrack := n ;
        while ntrack > 1 do
            ntrack := A094683(ntrack) ;
            a := a+1 ;
        end do:
        return a;
    end proc: # R. J. Mathar, Apr 19 2013
  • Mathematica
    js[n_] := If[ EvenQ[n], Floor[ Sqrt[n]], Floor[ Sqrt[n^3]]]; f[n_] := Length[ NestWhileList[js, n, # != 1 &]] - 1; Table[ f[n], {n, 99}] (* Robert G. Wilson v, Jun 10 2004 *)

Extensions

Corrected and extended by Jason Earls, Jun 09 2004

A093684 In binary representation: number of occurrences of n in n!.

Original entry on oeis.org

1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 3, 0, 1, 0, 2, 0, 1, 1, 1, 1, 2, 3, 2, 2, 2, 1, 1, 1, 3, 0, 2, 1, 3, 1, 1, 0, 1, 2, 2, 3, 3, 1, 1, 1, 1, 2, 2, 4, 3, 3, 3, 2, 2, 0, 3, 1, 5, 5, 6, 4, 1, 5, 2, 3, 2, 2, 4, 1, 1, 1, 4, 1, 1, 1, 2, 3, 3, 4, 5, 0, 3, 2, 1, 4, 3, 4, 5, 3, 2, 1, 2, 3, 3, 3, 3, 6, 2, 3, 4, 4, 2
Offset: 1

Views

Author

Reinhard Zumkeller, Apr 10 2004

Keywords

Comments

a(A093685(n)) = 0, a(A093686(n)) > 0.

Examples

			n=12->'1100', 12!=479001600->'11100100011001111110000000000' with three occurrences of '1100': '.1100....1100....1100........', therefore a(12)=3.
		

Crossrefs

Programs

  • Maple
    f:= proc(n) local L,Lf;
      L:= convert(convert(n,binary),string);
      Lf:= convert(convert(n!,binary),string);
      nops([StringTools:-SearchAll(L,Lf)])
    end proc:
    map(f, [$1..100]); # Robert Israel, May 20 2016
  • Mathematica
    non[n_]:=Module[{b=IntegerDigits[n,2],f=IntegerDigits[n!,2]}, Length[ Select[ Partition[ f,Length[b],1],#==b&]]]; Array[non,110] (* Harvey P. Dale, Jun 04 2014 *)

A093711 Numbers k such that in their binary representation not all numbers from 1 to k are contained in k!.

Original entry on oeis.org

5, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 27, 29, 31, 32, 36, 37, 38, 40, 41, 44, 45, 46, 47, 48, 49, 50, 52, 54, 55, 56, 57, 59, 60, 65, 67, 69, 71, 72, 74, 75, 76, 78, 79, 81, 82, 84, 85, 86, 87, 88, 89, 90, 91, 92, 95, 96, 97, 98, 99, 100, 101, 102
Offset: 1

Views

Author

Reinhard Zumkeller, Apr 11 2004

Keywords

Crossrefs

Complement of A093710.
A093685 \ {0} is a subsequence.

Formula

A092601(a(n)) < a(n).

A093686 In binary representation: numbers occurring at least once in their factorial.

Original entry on oeis.org

1, 2, 3, 4, 6, 7, 8, 9, 10, 12, 14, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79
Offset: 1

Views

Author

Reinhard Zumkeller, Apr 10 2004

Keywords

Comments

A093684(a(n)) > 0, complement of A093685.
Almost all numbers are included -- of the first 1000 numbers, only 14 -- i.e., 5, 11, 13, 15, 17, 31, 37, 55, 81, 164, 395, 513, 517, and 619 -- do not appear. In all likelihood, the density of such exceptions gets even smaller as the numbers get larger. - Harvey P. Dale, May 16 2025

Examples

			6!=1*2*3*4*5*6=720 -> '1011010000' where '110'=6 is contained:
'..110.....', therefore 6 is a term.
		

Crossrefs

Programs

  • Mathematica
    Select[Range[80],SequenceCount[IntegerDigits[#!,2],IntegerDigits[#,2]]>0&] (* Harvey P. Dale, May 16 2025 *)

A093826 In binary representation: least number, k, which occurs n times in its factorial.

Original entry on oeis.org

5, 1, 16, 12, 49, 58, 60, 110, 209, 117, 240, 430, 255, 1423, 921, 980, 511, 1847, 3737, 3692, 3998, 7265, 15267, 15651, 15722, 31457, 32659, 64248, 57927, 64448, 64171, 250068, 129013, 501578, 256159, 510732, 980930, 979883
Offset: 0

Views

Author

Keywords

Comments

Overlapping occurrences are counted. - Michael S. Branicky, May 01 2021
a(47) = 262143. - Michael S. Branicky, May 02 2021

Examples

			12!_b = 11100100011001111110000000000 and 12_b = 1100 and the later string appears thrice in the former string.
		

Crossrefs

Cf. A093685.

Programs

  • Mathematica
    f[n_] := ToString[ FromDigits[ IntegerDigits[n, 2]]]; g[n_] := Length[ StringPosition[ f[n! ], f[n]]]; a = Table[0, {30}]; Do[ b = g[n]; If[a[[b + 1]] == 0, a[[b + 1]] = n], {n, 29000}]; a
  • Python
    from itertools import count, takewhile
    def count_overlaps(subs, s):
      c = i = 0
      while i != -1:
        i = s.find(subs, i)
        if i != -1: c += 1; i += 1
      return c
    def afind(limit):
      kfact, adict = 1, dict()
      for k in range(1, limit+1):
        kb, kfact = bin(k)[2:], kfact * k
        kfactb = bin(kfact)[2:]
        n = count_overlaps(kb, kfactb)
        if n not in adict: adict[n] = k
      return [adict[n] for n in takewhile(lambda i: i in adict, count(0))]
    print(afind(16000))  # Michael S. Branicky, May 01 2021

Extensions

a(25)-a(37) from Michael S. Branicky, May 03 2021
Showing 1-5 of 5 results.