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.

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A284750 a(n) = least k > 0 such that k * n in factorial base representation contains only 0's and 1's.

Original entry on oeis.org

1, 1, 1, 2, 5, 1, 1, 1, 1, 3, 3, 2, 2, 9, 2, 2, 9, 7, 8, 6, 6, 33, 256, 1, 1, 1, 1, 26, 5, 1, 1, 1, 1, 149, 24, 4, 159, 4, 130, 3, 3, 3, 3, 118, 16, 128, 16, 3, 3, 3, 3, 14, 16, 16, 840, 13, 89, 15, 88, 2, 2, 12, 2, 2, 78, 11, 13, 76, 597, 12, 71, 2, 2, 555, 2
Offset: 1

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Author

Rémy Sigrist, Jun 25 2017

Keywords

Comments

a(n) = 1 iff n belongs to A059590.
a(a(n)) <= n for any n > 0.

Examples

			The first terms, alongside n*a(n) in decimal and factorial base, are:
n     a(n)  n*a(n)  n*a(n) in factorial base
--    ----  ------  ------------------------
1     1     1       1
2     1     2       1,0
3     1     3       1,1
4     2     8       1,1,0
5     5     25      1,0,0,1
6     1     6       1,0,0
7     1     7       1,0,1
8     1     8       1,1,0
9     1     9       1,1,1
10    3     30      1,1,0,0
11    3     33      1,1,1,1
12    2     24      1,0,0,0
13    2     26      1,0,1,0
14    9     126     1,0,1,0,0
15    2     30      1,1,0,0
16    2     32      1,1,1,0
17    9     153     1,1,1,1,1
18    7     126     1,0,1,0,0
19    8     152     1,1,1,1,0
20    6     120     1,0,0,0,0
		

Crossrefs

Programs

  • PARI
    isA059590(n) = my (r=2); while (n, if (n%r > 1, return (0), n\=r; r++)); return (1)
    a(n) = for (k=1, oo, if (isA059590(k*n), return (k)))

Formula

a(n) = A286820(n) / n.
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