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 1-6 of 6 results.

A023733 Numbers with no 3's in base-5 expansion.

Original entry on oeis.org

0, 1, 2, 4, 5, 6, 7, 9, 10, 11, 12, 14, 20, 21, 22, 24, 25, 26, 27, 29, 30, 31, 32, 34, 35, 36, 37, 39, 45, 46, 47, 49, 50, 51, 52, 54, 55, 56, 57, 59, 60, 61, 62, 64, 70, 71, 72, 74, 100, 101, 102, 104, 105, 106, 107, 109, 110, 111, 112, 114
Offset: 1

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Author

Keywords

Examples

			14 in base 5 is 24, which contains no 3's, so 14 is in the sequence.
15 in base 5 is 30, so 15 is not in the sequence.
		

Crossrefs

Programs

Formula

Sum_{n>=2} 1/a(n) = 7.2918685472993284072384543509909968409572571215800451577936556651148540560895813691253670323741759722063... (calculated using Baillie and Schmelzer's kempnerSums.nb, see Links). - Amiram Eldar, Apr 14 2025

A023725 Numbers with no 1's in their base-5 expansion.

Original entry on oeis.org

0, 2, 3, 4, 10, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 24, 50, 52, 53, 54, 60, 62, 63, 64, 65, 67, 68, 69, 70, 72, 73, 74, 75, 77, 78, 79, 85, 87, 88, 89, 90, 92, 93, 94, 95, 97, 98, 99, 100, 102, 103, 104, 110, 112, 113, 114, 115, 117, 118, 119, 120
Offset: 1

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Author

Keywords

Crossrefs

Programs

  • Maple
    seq(`if`(numboccur(1,convert(n,base,5))=0,n,NULL),n=0..127); # Nathaniel Johnston, Jun 27 2011
  • Mathematica
    Select[ Range[ 0, 125 ], (Count[ IntegerDigits[ #, 5 ], 1 ]==0)& ]
    Select[Range[0, 120], DigitCount[#, 5, 1] == 0 &] (* Amiram Eldar, Apr 14 2025 *)
  • PARI
    is(n)=while(n>1, if(n%5==1, return(0)); n\=5); 1 \\ Charles R Greathouse IV, Feb 12 2017

Formula

Sum_{n>=2} 1/a(n) = 4.7113203882192880160403245816366085015069192113921100121384809791433027046475062716543062654277431569224... (calculated using Baillie and Schmelzer's kempnerSums.nb, see Links). - Amiram Eldar, Apr 14 2025

A023729 Numbers with no 2's in their base-5 expansion.

Original entry on oeis.org

0, 1, 3, 4, 5, 6, 8, 9, 15, 16, 18, 19, 20, 21, 23, 24, 25, 26, 28, 29, 30, 31, 33, 34, 40, 41, 43, 44, 45, 46, 48, 49, 75, 76, 78, 79, 80, 81, 83, 84, 90, 91, 93, 94, 95, 96, 98, 99, 100, 101, 103, 104, 105, 106, 108, 109, 115, 116, 118, 119, 120, 121
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Maple
    seq(`if`(numboccur(2,convert(n,base,5))=0,n,NULL),n=0..127); # Nathaniel Johnston, Jun 27 2011
  • Mathematica
    Select[ Range[ 0, 125 ], (Count[ IntegerDigits[ #, 5 ], 2 ]==0)& ]
    Select[Range[0, 120], DigitCount[#, 5, 2] == 0 &] (* Amiram Eldar, Apr 14 2025 *)
  • PARI
    is(n)=while(n>2, if(n%5==2, return(0)); n\=5); 1 \\ Charles R Greathouse IV, Feb 12 2017

Formula

Sum_{n>=2} 1/a(n) = 6.4926328481629227744899858111920644967528391159751448517967690160220746453627777857879224296518328062481... (calculated using Baillie and Schmelzer's kempnerSums.nb, see Links). - Amiram Eldar, Apr 14 2025

A382415 Numbers with at least one zero in their base-5 representation.

Original entry on oeis.org

0, 5, 10, 15, 20, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 51, 52, 53, 54, 55, 60, 65, 70, 75, 76, 77, 78, 79, 80, 85, 90, 95, 100, 101, 102, 103, 104, 105, 110, 115, 120, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145
Offset: 1

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Author

Paolo Xausa, Mar 25 2025

Keywords

Crossrefs

Cf. analogous sequences in other bases: A062289 (base 2), A081605 (base 3), A196032 (base 4), A382416 (base 6), A382413 (base 7), A382417 (base 8), A382418 (base 9), A011540 (base 10).
Cf. A007091, A023721 (complement), A023722.

Programs

  • Mathematica
    Select[Range[0, 150], DigitCount[#, 5, 0] > 0 &]

A249102 Numbers with no 1's in base-7 expansion.

Original entry on oeis.org

0, 2, 3, 4, 5, 6, 14, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 44, 45, 46, 47, 48, 98, 100, 101, 102, 103, 104, 112, 114, 115, 116, 117, 118, 119, 121, 122, 123, 124, 125, 126, 128, 129, 130, 131, 132, 133
Offset: 1

Views

Author

Zak Seidov, Oct 21 2014

Keywords

Examples

			14_10 = 20_7, 16_10 = 22_10, 17_10 = 23_7.
14 in base 7 is 20, which contains no 1s, so 14 is in the sequence.
15 in base 7 is 21, which contains one 1, so 15 is not in the sequence.
16 in base 7 is 22, so 16 is in the sequence.
		

Crossrefs

Subsequence of A047306. Cf. A023721, A023725, A023729, A023733, A005823. This sequence has no terms in common with A016993.

Programs

  • Mathematica
    Select[Range[0, 200], FreeQ[IntegerDigits[#, 7], 1] &] (* Seidov *)
    Select[Range[0, 139], DigitCount[#, 7, 1] == 0 &] (* Alonso del Arte, Oct 26 2014 *)
  • PARI
    fromdigits(v, b=10)=subst(Pol(v), 'x, b) \\ needed for gp < 2.63 or so
    a(n)=a(n)=fromdigits(apply(k->if(k, k+1, 0), digits(n, 6)),7) \\ Charles R Greathouse IV, Oct 30 2014

A382412 Numbers with no zeros in their base-7 representation.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 89, 90
Offset: 1

Views

Author

Paolo Xausa, Mar 24 2025

Keywords

Crossrefs

Cf. zeroless numbers in other bases: A126646 (base 2), A032924 (base 3), A023705 (base 4), A023721 (base 5), A248910 (base 6), A255805 (base 8), A255808 (base 9), A052382 (base 10).
Cf. A007093, A043393, A249102, A382413 (complement).

Programs

  • Mathematica
    Select[Range[100], DigitCount[#, 7, 0] == 0 &]
Showing 1-6 of 6 results.