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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A284963 Numbers with digits 3 and 8 only.

Original entry on oeis.org

3, 8, 33, 38, 83, 88, 333, 338, 383, 388, 833, 838, 883, 888, 3333, 3338, 3383, 3388, 3833, 3838, 3883, 3888, 8333, 8338, 8383, 8388, 8833, 8838, 8883, 8888, 33333, 33338, 33383, 33388, 33833, 33838, 33883, 33888, 38333, 38338, 38383, 38388, 38833, 38838
Offset: 1

Views

Author

Jaroslav Krizek, Apr 06 2017

Keywords

Crossrefs

Prime terms are in A020464.
Numbers with digits 3 and k only for k = 0 - 2 and 4 - 9: A169966 (k = 0), A032917 (k = 1), A032810 (k = 2), A032834 (k = 4), A284379 (k = 5), A284633 (k = 6), A143967 (k = 7), this sequence (k = 8), A284964 (k = 9).

Programs

  • Magma
    [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {3, 8}]
  • Mathematica
    Table[FromDigits/@Tuples[{3,8},n],{n,5}]//Flatten (* Harvey P. Dale, Mar 23 2021 *)

A284964 Numbers with digits 3 and 9 only.

Original entry on oeis.org

3, 9, 33, 39, 93, 99, 333, 339, 393, 399, 933, 939, 993, 999, 3333, 3339, 3393, 3399, 3933, 3939, 3993, 3999, 9333, 9339, 9393, 9399, 9933, 9939, 9993, 9999, 33333, 33339, 33393, 33399, 33933, 33939, 33993, 33999, 39333, 39339, 39393, 39399, 39933, 39939
Offset: 1

Views

Author

Jaroslav Krizek, Apr 06 2017

Keywords

Comments

All terms > 3 are composite.

Crossrefs

Cf. Numbers with digits 3 and k only for k = 0 - 2 and 4 - 9: A169966 (k = 0), A032917 (k = 1), A032810 (k = 2), A032834 (k = 4), A284379 (k = 5), A284633 (k = 6), A143967 (k = 7), A284963 (k = 8), this sequence (k = 9).

Programs

  • Magma
    [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {3, 9}]
  • Mathematica
    Table[FromDigits/@Tuples[{3,9},n],{n,5}]//Flatten (* Harvey P. Dale, Sep 20 2022 *)

Formula

a(n) = 3 * A032917(n).

A335787 Emirps containing only the digits 1 and 3.

Original entry on oeis.org

13, 31, 113, 311, 113131, 131311, 1131131, 1133131, 1133333, 1311311, 1313311, 1331333, 1333313, 3111313, 3131113, 3133331, 3331331, 3333311, 11113111, 11131111, 11311133, 11313311, 11331311, 11333131, 13131133, 13133311, 31111313, 31311113, 33111311, 33113131
Offset: 1

Views

Author

Daniel Starodubtsev, Jun 23 2020

Keywords

Links

Crossrefs

Intersection of A006567 and A032917.
Subsequence of A020451.

Programs

  • Mathematica
    Select[Flatten[Table[FromDigits[#, 10] & /@ Tuples[{1, 3}, n], {n, 8}]], # != (r = IntegerReverse[#]) && PrimeQ[#] && PrimeQ[r] &] (* Amiram Eldar, Jun 23 2020 after Vincenzo Librandi at A032917 *)
Previous Showing 11-13 of 13 results.

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

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