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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A321683 Numbers with distinct digits in primorial base.

Original entry on oeis.org

0, 1, 2, 4, 5, 10, 13, 14, 19, 20, 22, 23, 25, 26, 28, 29, 52, 58, 79, 80, 85, 86, 95, 100, 103, 104, 115, 116, 118, 119, 125, 130, 133, 134, 139, 140, 142, 143, 155, 160, 163, 164, 169, 170, 172, 173, 175, 176, 178, 179, 185, 190, 193, 194, 199, 200, 202, 203
Offset: 1

Views

Author

Rémy Sigrist, Nov 17 2018

Keywords

Comments

This sequence is a variant of A010784 (numbers with distinct digits in decimal). The final term of that sequence is 9876543210. This sequence, by contrast, has infinitely many terms (for example, all the terms of A057588 belong to this sequence).

Examples

			13 in primorial base is 201, which has no repeated digits, hence 13 is in the sequence.
14 in primorial base is 210, which has no repeated digits, hence 14 is also in the sequence.
15 in primorial base is 211, so 15 is not in the sequence on account of the digit 1 appearing twice in its primorial base representation.
		

Crossrefs

See A321682 for the factorial base variant.

Programs

  • Mathematica
    q[n_] := Module[{k = n, p = 2, s = {}, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, AppendTo[s, r]; p = NextPrime[p]]; UnsameQ @@ s]; Select[Range[0, 210], q] (* Amiram Eldar, Mar 13 2024 *)
  • PARI
    is(n) = my (s=0); forprime (p=2, oo, if (n==0, return (1)); my (d=n%p); if (bittest(s,d), return (0), s+=2^d; n\=p))

A322845 Lexicographically earliest sequence of distinct positive terms such that the sum of two consecutive terms has distinct digits in factorial base.

Original entry on oeis.org

1, 3, 2, 8, 5, 9, 4, 6, 7, 12, 10, 13, 33, 34, 43, 24, 22, 45, 23, 44, 38, 29, 17, 50, 18, 28, 39, 46, 21, 25, 42, 26, 20, 47, 30, 16, 51, 31, 15, 52, 49, 19, 27, 40, 37, 48, 53, 14, 32, 35, 11, 56, 54, 55, 60, 41, 36, 65, 173, 182, 174, 64, 291, 170, 68, 287
Offset: 1

Views

Author

Rémy Sigrist, Dec 29 2018

Keywords

Comments

In other words, for any n > 0, a(n) + a(n+1) belongs to A321682.
Apparently, all the positive integers appear in the sequence.
This sequence has interesting graphical features (see scatterplots in Links section).
This sequence is to A321682 what A228730 is to A002113.

Examples

			The first terms, alongside the factorial representation of a(n)+a(n+1), are:
  n   a(n)  fact(a(n)+a(n+1))
  --  ----  -----------------
   1     1              (2,0)
   2     3              (2,1)
   3     2            (1,2,0)
   4     8            (2,0,1)
   5     5            (2,1,0)
   6     9            (2,0,1)
   7     4            (1,2,0)
   8     6            (2,0,1)
   9     7            (3,0,1)
  10    12            (3,2,0)
  11    10            (3,2,1)
  12    13          (1,3,2,0)
		

Crossrefs

Programs

  • C
    // See Links section.

A307710 a(n) is the determinant of the Vandermonde matrix of the digits of n in factorial base.

Original entry on oeis.org

1, 1, -1, 0, -2, -1, 0, 0, 0, 0, 2, 0, 0, 2, -2, 0, 0, 0, 0, 6, -6, 0, -6, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, -12, 0, 0, 0, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0
Offset: 0

Views

Author

Rémy Sigrist, Apr 23 2019

Keywords

Comments

This sequence is a variant of A307651, and has infinitely many nonzero terms.

Examples

			                                    | 3^0 3^1 2^2 |
a(22) = a(3*3! + 2*2! + 0*1!) = det | 2^0 2^1 2^2 | = -6.
                                    | 0^0 0^1 0^2 |
		

Crossrefs

See A307651 for the decimal variant.

Programs

  • PARI
    a(n) = my (d=[]); for (r=2, oo, if (n, d=concat(n%r,d); n\=r, return (matdet(matrix(#d, #d, r, c, d[r]^(c-1))))))

Formula

a(n) != 0 iff n belongs to A321682.
Showing 1-3 of 3 results.