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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A053334 a(n) contains n digits (either '1' or '6') and is divisible by 2^n.

Original entry on oeis.org

6, 16, 616, 1616, 11616, 111616, 6111616, 16111616, 616111616, 1616111616, 61616111616, 661616111616, 1661616111616, 61661616111616, 661661616111616, 6661661616111616, 66661661616111616, 666661661616111616
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Programs

  • Mathematica
    nxt[{n_,a_}]:={n+1,a+10^n (6-5*Mod[a/2^n,2])}; NestList[nxt,{1,6},20][[;;,2]] (* Harvey P. Dale, Aug 20 2025 *)

Formula

a(n)=a(n-1)+10^(n-1)*(6-5*[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 6, if not then n-th term begins with a 1.

A053335 a(n) contains n digits (either '3' or '6') and is divisible by 2^n.

Original entry on oeis.org

6, 36, 336, 6336, 66336, 366336, 6366336, 36366336, 636366336, 3636366336, 33636366336, 333636366336, 3333636366336, 33333636366336, 633333636366336, 3633333636366336, 33633333636366336, 333633333636366336
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Formula

a(n)=a(n-1)+10^(n-1)*(6-3*[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 6, if not then n-th term begins with a 3.

A053336 a(n) contains n digits (either '5' or '6') and is divisible by 2^n.

Original entry on oeis.org

6, 56, 656, 6656, 66656, 566656, 6566656, 66566656, 666566656, 6666566656, 56666566656, 656666566656, 6656666566656, 66656666566656, 566656666566656, 6566656666566656, 56566656666566656, 556566656666566656
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Block[{a = {6}, k, m, w}, Do[k = 1; If[Mod[a[[-1]], 2^i] == 0, Set[w, Prepend[ConstantArray[5, i - 1], 6]], Set[w, ConstantArray[5, i]]]; While[Mod[Set[m, FromDigits[w + PadLeft[IntegerDigits[k, 2], i]]], 2^i] != 0, k++]; AppendTo[a, m], {i, 2, 18}]; a] (* Michael De Vlieger, Dec 10 2020 *)

Formula

a(n) = a(n-1)+10^(n-1)*(6-[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 6, if not then n-th term begins with a 5.
Conjecture: a(n) = 10^n - A035014(n). - J. Lowell, Nov 16 2020

A053337 a(n) contains n digits (either '6' or '7') and is divisible by 2^n.

Original entry on oeis.org

6, 76, 776, 7776, 67776, 667776, 6667776, 66667776, 766667776, 6766667776, 66766667776, 666766667776, 7666766667776, 77666766667776, 777666766667776, 7777666766667776, 77777666766667776, 777777666766667776
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Select[FromDigits/@Tuples[{6,7},n],Divisible[#,2^IntegerLength[ #]]&], {n,18}]//Flatten (* Harvey P. Dale, Jul 10 2016 *)

Formula

a(n)=a(n-1)+10^(n-1)*(6+[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 6, if not then n-th term begins with a 7.

A053377 a(n) contains n digits (either '3' or '8') and is divisible by 2^n.

Original entry on oeis.org

8, 88, 888, 3888, 33888, 333888, 3333888, 83333888, 383333888, 3383333888, 33383333888, 833383333888, 8833383333888, 88833383333888, 888833383333888, 8888833383333888, 88888833383333888, 888888833383333888
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Flatten[Table[Select[FromDigits/@Tuples[{3,8},n],Divisible[#,2^n]&],{n,18}]] (* Harvey P. Dale, Dec 25 2015 *)

Formula

a(n)=a(n-1)+10^(n-1)*(8-5*[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with an 8, if not then n-th term begins with a 3.

A053378 a(n) contains n digits (either '5' or '8') and is divisible by 2^n.

Original entry on oeis.org

8, 88, 888, 5888, 85888, 885888, 8885888, 58885888, 558885888, 8558885888, 58558885888, 858558885888, 5858558885888, 85858558885888, 585858558885888, 5585858558885888, 55585858558885888, 855585858558885888
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Formula

a(n)=a(n-1)+10^(n-1)*(8-3*[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with an 8, if not then n-th term begins with a 5.

A053379 a(n) contains n digits (either '7' or '8') and is divisible by 2^n.

Original entry on oeis.org

8, 88, 888, 7888, 77888, 877888, 7877888, 87877888, 787877888, 8787877888, 88787877888, 888787877888, 8888787877888, 88888787877888, 788888787877888, 8788888787877888, 88788888787877888, 888788888787877888
Offset: 1

Views

Author

Henry Bottomley, Mar 06 2000

Keywords

Crossrefs

Formula

a(n)=a(n-1)+10^(n-1)*(8-[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with an 8, if not then n-th term begins with a 7.

A241882 Numbers with d digits that are divisible by 2^d and have at most 2 distinct digits: exactly one even digit and at most one odd digit.

Original entry on oeis.org

2, 4, 6, 8, 12, 16, 32, 36, 44, 52, 56, 72, 76, 88, 92, 96, 112, 144, 232, 272, 336, 344, 544, 552, 616, 656, 696, 744, 776, 888, 944, 992, 1616, 1888, 2112, 2272, 2992, 3232, 3344, 3888, 4144, 4544, 4944, 5552, 5888, 6336, 6656, 7744, 7776, 7888, 9696, 9888
Offset: 1

Views

Author

J. Lowell, Apr 30 2014

Keywords

Comments

Union of 20 different sequences, all of which are defined as "a(n) contains n digits (either [any odd digit] or [any nonzero even digit] and is divisible by 2^n)."
Subsequence of A050622. - Michel Marcus, May 07 2014

Examples

			24 is not in the sequence because it has distinct even digits.
		

Crossrefs

Cf. A035014, A053312-A053318, A053332-A053338, A053376-A053380 (sequences whose union is this sequence).

Programs

  • PARI
    isok(n) = {digs = digits(n); d = #digs; if (n % 2^d, return (0)); sd = Set(digs); if (#sd > 2, return (0)); if (#sd < 2, return (1)); ((sd[1] % 2) + (sd[2] % 2)) == 1;} \\ Michel Marcus, May 02 2014

Extensions

More terms from Michel Marcus, May 02 2014

A284924 a(n) is the least n-digit multiple of 5^n using the decimal digits {5, 6, 7, 8, 9} exclusively.

Original entry on oeis.org

5, 75, 875, 6875, 96875, 796875, 6796875, 66796875, 966796875, 5966796875, 65966796875, 865966796875, 8865966796875, 68865966796875, 868865966796875, 8868865966796875, 78868865966796875, 578868865966796875, 7578868865966796875, 87578868865966796875
Offset: 1

Views

Author

J. Lowell, Apr 05 2017

Keywords

Examples

			a(2) = 75 because 75 is divisible by 5^2 (25*3=75) and uses only digits in the 5-9 interval.
		

Crossrefs

Extensions

More terms from Alois P. Heinz, Apr 06 2017
Previous Showing 21-29 of 29 results.