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 1-4 of 4 results.

A145256 a(n) = the smallest integer > n that is non-coprime to n and has the same number of 1's in its binary representation as n has.

Original entry on oeis.org

4, 6, 8, 10, 9, 14, 16, 12, 12, 22, 18, 26, 21, 27, 32, 34, 20, 38, 24, 28, 26, 46, 33, 35, 28, 30, 35, 58, 39, 62, 64, 36, 36, 42, 40, 74, 42, 45, 48, 82, 44, 86, 50, 51, 54, 94, 66, 56, 52, 54, 56, 106, 57, 110, 70, 60, 60, 118, 75, 122, 93, 111, 128, 80, 68, 134, 72, 81, 74
Offset: 2

Views

Author

Leroy Quet, Oct 05 2008

Keywords

Comments

a(n) <= 2n since 2n is trivially a multiple of n and multiplying a number by 2 adds a 0 in base 2. - Stefan Steinerberger, Oct 17 2008

Links

Crossrefs

Cf. A145254, A145255, A145257.

Programs

  • Mathematica
    a[n_] := Block[{}, i = n + 1; While[GCD[i, n] == 1 || Not[DigitCount[n, 2, 1] == DigitCount[i, 2, 1]], i++ ]; i]; Table[a[n], {n, 2, 100}] (* Stefan Steinerberger, Oct 17 2008 *)
  • PARI
    a(n) = for (m=n+1, oo, if (gcd(m,n)>1 && hammingweight(m)==hammingweight(n), return (m))) \\ Rémy Sigrist, Feb 06 2020

Extensions

Edited and corrected by Stefan Steinerberger, Oct 17 2008

A145254 a(n) = the smallest positive integer that is non-coprime to n and has the same number of 1's in its binary representation as n.

Original entry on oeis.org

2, 3, 2, 5, 3, 7, 2, 3, 5, 11, 3, 13, 7, 15, 2, 17, 3, 19, 5, 7, 11, 23, 3, 25, 13, 15, 7, 29, 15, 31, 2, 3, 6, 7, 3, 37, 14, 15, 5, 41, 7, 43, 11, 15, 23, 47, 3, 7, 14, 15, 13, 53, 15, 55, 7, 15, 29, 59, 15, 61, 31, 63, 2, 5, 3, 67, 6, 21, 7, 71, 3, 73, 14, 15, 14, 77, 15, 79, 5, 21, 14, 83
Offset: 2

Views

Author

Leroy Quet, Oct 05 2008

Keywords

Links

Crossrefs

Cf. A145255, A145256, A145257.

Programs

  • Mathematica
    Table[Function[k, SelectFirst[Range[2, n], And[! CoprimeQ[#, n], DigitCount[#, 2, 1] == k] &]]@ DigitCount[n, 2, 1], {n, 2, 83}] (* Michael De Vlieger, Oct 26 2017 *)
  • PARI
    a(n) = {my(k = 1, hn = hammingweight(n)); while ((hammingweight(k) != hn) || (gcd(n, k) == 1), k++); k;} \\ Michel Marcus, Oct 27 2017

Extensions

Extended by Ray Chandler, Nov 03 2008

A145255 a(n) = the smallest positive integer that is non-coprime to n and has the same number of 0's in its binary representation as n has.

Original entry on oeis.org

2, 3, 4, 5, 2, 7, 8, 9, 4, 11, 4, 13, 2, 3, 16, 17, 8, 19, 8, 9, 4, 23, 8, 10, 4, 6, 4, 29, 2, 31, 32, 33, 16, 20, 16, 37, 8, 9, 16, 41, 8, 43, 8, 9, 4, 47, 16, 35, 8, 9, 8, 53, 4, 5, 8, 9, 4, 59, 4, 61, 2, 3, 64, 65, 32, 67, 32, 33, 16, 71, 32, 73, 16, 18, 16, 35, 8, 79, 32, 33, 16, 83, 16
Offset: 2

Views

Author

Leroy Quet, Oct 05 2008

Keywords

Links

Crossrefs

Cf. A145254, A145256, A145257.

Programs

  • Mathematica
    Table[Function[k, SelectFirst[Range[2, n], And[! CoprimeQ[#, n], DigitCount[#, 2, 0] == k] &]]@ DigitCount[n, 2, 0], {n, 2, 84}] (* Michael De Vlieger, Oct 26 2017 *)

Extensions

Extended by Ray Chandler, Nov 03 2008

A161397 a(n) = the smallest positive integer that contains the same number of (non-leading) 0's as n when a(n) and n are written in binary, is not coprime to n, and is not a divisor of n.

Original entry on oeis.org

6, 15, 10, 30, 14, 63, 18, 12, 4, 55, 9, 247, 6, 63, 34, 85, 8, 57, 8, 9, 4, 253, 18, 10, 4, 6, 10, 1015, 14, 1023, 66, 36, 16, 20, 16, 185, 8, 9, 16, 205, 8, 215, 8, 10, 4, 14335, 33, 35, 8, 9, 8, 159, 4, 30, 18, 9, 4, 767, 9, 4087, 6, 15, 130, 80, 32, 201, 32, 33, 16, 213, 32, 730
Offset: 2

Views

Author

Leroy Quet, Jun 09 2009

Keywords

Links

Crossrefs

Cf. A145257, A161396.

Extensions

a(1) is undefined; offset corrected by Hagen von Eitzen, Jun 20 2009
Corrected and extended using terms from b-file. - N. J. A. Sloane, Aug 31 2009
Showing 1-4 of 4 results.

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