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.

A328840 Numbers with no digit 1 in their primorial base expansion (A049345).

Original entry on oeis.org

0, 4, 12, 16, 18, 22, 24, 28, 60, 64, 72, 76, 78, 82, 84, 88, 90, 94, 102, 106, 108, 112, 114, 118, 120, 124, 132, 136, 138, 142, 144, 148, 150, 154, 162, 166, 168, 172, 174, 178, 180, 184, 192, 196, 198, 202, 204, 208, 420, 424, 432, 436, 438, 442, 444, 448, 480, 484, 492, 496, 498, 502, 504, 508, 510, 514, 522, 526
Offset: 1

Views

Author

Antti Karttunen, Nov 07 2019

Keywords

Comments

Numbers for which the least missing nonzero digit (A329028) in their primorial base expansion is 1.

Crossrefs

Cf. A049345.
Positions of ones in A329028.
Cf. also A328574 and A329027.
Cf. A255411 for an analogous sequence.

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]]; FreeQ[s, 1]]; Select[Range[0, 600], q] (* Amiram Eldar, Mar 06 2024 *)
  • PARI
    A329028(n) = { my(m=Map(), p=2); while(n, mapput(m,(n%p),1); n = n\p; p = nextprime(1+p)); for(k=1,oo,if(!mapisdefined(m,k),return(k))); };
    isA328840(n) = (1 == A329028(n));

A329027 The least missing digit in the primorial base expansion of n. Only significant digits are considered, as the leading zeros are ignored.

Original entry on oeis.org

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

Views

Author

Antti Karttunen, Nov 03 2019

Keywords

Comments

For n = 0 the value is ambiguous, thus the sequence starts from n=1.

Examples

			19 in primorial base (A049345) is written as "301". The least missing digit is 2, thus a(19) = 2.
		

Crossrefs

Cf. A328574 (after its initial term, gives the positions of zeros in this sequence), A328840 (after its initial term, gives the positions of ones in this sequence).

Programs

  • Mathematica
    a[n_] := Module[{k = n, p = 2, s = {}, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, AppendTo[s, r]; p = NextPrime[p]]; Min[Complement[Range[0, Max[s]+1], s]]]; Array[a, 100] (* Amiram Eldar, Mar 13 2024 *)
  • PARI
    A329027(n) = { my(m=Map(), p=2); while(n, mapput(m,(n%p),1); n = n\p; p = nextprime(1+p)); for(k=0,oo,if(!mapisdefined(m,k),return(k))); };

A328573 a(n) = A328475(n) / A328572(n).

Original entry on oeis.org

1, 1, 3, 1, 3, 1, 5, 5, 15, 1, 15, 1, 5, 5, 15, 1, 15, 1, 5, 5, 15, 1, 15, 1, 5, 5, 15, 1, 15, 1, 7, 7, 21, 7, 21, 7, 35, 35, 105, 1, 105, 1, 35, 35, 105, 1, 105, 1, 35, 35, 105, 1, 105, 1, 35, 35, 105, 1, 105, 1, 7, 7, 21, 7, 21, 7, 35, 35, 105, 1, 105, 1, 35, 35, 105, 1, 105, 1, 35, 35, 105, 1, 105, 1, 35, 35, 105, 1, 105, 1, 7, 7, 21, 7, 21
Offset: 0

Views

Author

Antti Karttunen, Oct 20 2019

Keywords

Crossrefs

Cf. A328574 (positions of 1's).

Programs

  • PARI
    A328475(n) = { my(m=1, p=2, y=1); while(n, if(n%p, m *= p^((n%p)-y), y=0); n = n\p; p = nextprime(1+p)); (m); };
    A328572(n) = { my(m=1, p=2); while(n, if(n%p, m *= p^((n%p)-1)); n = n\p; p = nextprime(1+p)); (m); };
    A328573(n) = (A328475(n) / A328572(n));

Formula

a(n) = A328475(n) / A328572(n).

A341433 Numbers that are divisible by the product of their digits in primorial base representation.

Original entry on oeis.org

1, 3, 9, 21, 39, 51, 99, 249, 261, 309, 669, 729, 2559, 2571, 2619, 2979, 3051, 4239, 7179, 7191, 32589, 32601, 32649, 32661, 33009, 33021, 37209, 37269, 37629, 51489, 92649, 92709, 93069, 97281, 272889, 274509, 543099, 543111, 543159, 543519, 543591, 544779
Offset: 1

Views

Author

Amiram Eldar, Feb 11 2021

Keywords

Comments

The primorial base repunits (A143293) are all terms since their product of digits in primorial base is 1.
All the terms are zeroless in primorial base, and therefore they are terms of A328574. In particular, since the last digit of even numbers in primorial base is 0, all the terms are odd numbers.

Examples

			9 is a term since 9 in primorial base is 111 (9 = 3! + 2! + 1!) and 9 is divisible by 1*1*1 = 1.
		

Crossrefs

A143293 is a subsequence.
Subsequence of A328574.

Programs

  • Mathematica
    max = 12; bases = Prime@Range[max, 1, -1]; nmax = Times @@ bases - 1; q[n_] := FreeQ[(d = IntegerDigits[n, MixedRadix[bases]]), 0] && Divisible[n, Times @@ d]; Select[Range[1, 10^5, 2], q]

A355037 a(n) is the product of the digits of n in primorial base.

Original entry on oeis.org

0, 1, 0, 1, 0, 2, 0, 0, 0, 1, 0, 2, 0, 0, 0, 2, 0, 4, 0, 0, 0, 3, 0, 6, 0, 0, 0, 4, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 2, 0, 4, 0, 0, 0, 3, 0, 6, 0, 0, 0, 4, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 4, 0, 0, 0, 4, 0, 8, 0, 0, 0, 6, 0, 12, 0, 0, 0
Offset: 0

Views

Author

Rémy Sigrist, Jun 16 2022

Keywords

Examples

			The first terms, alongside the digits of n in primorial base, are:
  n   a(n)  pr(n)
  --  ----  -----
   0     0      0
   1     1      1
   2     0    1_0
   3     1    1_1
   4     0    2_0
   5     2    2_1
   6     0  1_0_0
   7     0  1_0_1
   8     0  1_1_0
   9     1  1_1_1
  10     0  1_2_0
  11     2  1_2_1
  12     0  2_0_0
  13     0  2_0_1
  14     0  2_1_0
  15     2  2_1_1
		

Crossrefs

Programs

  • PARI
    a(n) = { my (p=1); forprime (r=2, oo, p*=n%r; n\=r; if (p==0 || n==0, return (p))) }

Formula

a(n) = 1 iff n belongs to A143293.
a(n) > 0 iff n belongs to A328574 \ {0}.
Showing 1-5 of 5 results.