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 1-8 of 8 results.

A011557 Powers of 10: a(n) = 10^n.

Original entry on oeis.org

1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000, 10000000000, 100000000000, 1000000000000, 10000000000000, 100000000000000, 1000000000000000, 10000000000000000, 100000000000000000, 1000000000000000000
Offset: 0

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Author

Keywords

Comments

Same as Pisot sequences E(1, 10), L(1, 10), P(1, 10), T(1, 10). Essentially same as Pisot sequences E(10, 100), L(10, 100), P(10, 100), T(10, 100). See A008776 for definitions of Pisot sequences.
Same as k^n in base k. - Dominick Cancilla, Aug 02 2010 [Corrected by Jianing Song, Sep 17 2022]
The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n >= 1, a(n) equals the number of 10-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011
Smallest n+1 digit number greater than 0 (with offset 0). - Wesley Ivan Hurt, Jan 17 2014
Numbers with digit sum = 1, or, A007953(a(n)) = 1. - Reinhard Zumkeller, Jul 17 2014
Does not satisfy Benford's law. - N. J. A. Sloane, Feb 14 2017

References

  • Philip Morrison et al., Powers of Ten, Scientific American Press, 1982 and later editions.
  • S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.

Crossrefs

Cf. A178501: this sequence with 0 prefixed.
Row 5 of A329332.

Programs

Formula

a(n) = 10^n.
a(n) = 10*a(n-1).
G.f.: 1/(1-10*x).
E.g.f.: exp(10*x).
A000005(a(n)) = A000290(n+1). - Reinhard Zumkeller, Mar 04 2007
a(n) = 60^n/6^n = A159991(n)/A000400(n). - Reinhard Zumkeller, May 02 2009
a(n) = A178501(n+1); for n > 0: a(n) = A178500(n). - Reinhard Zumkeller, May 28 2010
Sum_{n>0} 1/a(n) = 1/9 = A000012. - Stefano Spezia, Apr 28 2024

Extensions

Links to "Powers of Ten" books and videos added by N. J. A. Sloane, Nov 07 2009

A029793 Numbers k such that k and k^2 have the same set of digits.

Original entry on oeis.org

0, 1, 10, 100, 1000, 4762, 4832, 10000, 10376, 10493, 11205, 12385, 12650, 14829, 22450, 23506, 24605, 26394, 34196, 36215, 47620, 48302, 48320, 49827, 64510, 68474, 71205, 72510, 72576, 74510, 74528, 79286, 79603, 79836, 94583, 94867, 96123, 98376
Offset: 1

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Author

Keywords

Comments

This sequence has density 1: almost all numbers k have all 10 digits in both k and k^2. - Franklin T. Adams-Watters, Jun 28 2011

Examples

			{0, 1, 3, 4, 9} = digits of a(10) = 10493 and of 10493^2 = 110103049;
{0, 1, 2, 5, 6} = digits of a(100) = 162025 and of 162025^2 = 26252100625;
{0, 1, 3, 4, 6, 7, 8} = digits of a(1000) = 1764380 and of 1764380^2 = 3113036784400;
{1, 2, 3, 4, 7, 8, 9} = digits of a(10000) = 14872239 and of 14872239^2 = 221183492873121.
		

Crossrefs

Programs

  • Haskell
    import Data.List (nub, sort)
    a029793 n = a029793_list !! (n-1)
    a029793_list = filter (\x -> digs x == digs (x^2)) [0..]
       where digs = sort . nub . show
    -- Reinhard Zumkeller, Jun 27 2011
    
  • Magma
    [ n: n in [0..10^5] | Set(Intseq(n)) eq Set(Intseq(n^2)) ];  // Bruno Berselli, Jun 28 2011
    
  • Maple
    seq(`if`(convert(convert(n,base,10),set) = convert(convert(n^2,base,10),set), n, NULL), n=0..100000); # Nathaniel Johnston, Jun 28 2011
  • Mathematica
    digitSet[n_] := Union[IntegerDigits[n]]; Select[Range[0, 99000], digitSet[#] == digitSet[#^2] &] (* Jayanta Basu, Jun 02 2013 *)
  • PARI
    isA029793(n)=Set(Vec(Str(n)))==Set(Vec(Str(n^2))) \\ Charles R Greathouse IV, Jun 28 2011
    
  • Scala
    (0L to 99999L).filter(n => n.toString.toCharArray.toSet == (n * n).toString.toCharArray.toSet) // Alonso del Arte, Jan 19 2020

A178500 a(n) = 10^n * signum(n).

Original entry on oeis.org

0, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000, 10000000000, 100000000000, 1000000000000, 10000000000000, 100000000000000, 1000000000000000, 10000000000000000, 100000000000000000, 1000000000000000000, 10000000000000000000, 100000000000000000000
Offset: 0

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Author

Reinhard Zumkeller, May 28 2010

Keywords

Comments

a(n-1) is the minimum difference between an n-digit number (written in base 10, nonzero leading digit) and the product of its digits. For n > 1, it is also a number meeting that bound. See A070565. - Devin Akman, Apr 17 2019

Crossrefs

Programs

Formula

a(n) = A011557(n)*A057427(n).
For n > 0, a(n) = A011557(n).
a(n) = 10*A178501(n).
a(n) = A000533(n) - 1.
A061601(a(n)) = A109002(n+1).
From Elmo R. Oliveira, Jul 21 2025: (Start)
G.f.: 10*x/(1-10*x).
E.g.f.: 2*exp(5*x)*sinh(5*x).
a(n) = 10*a(n-1) for n > 1. (End)

A258682 Remove from n^2 all digits of n from left to right, in decimal representation.

Original entry on oeis.org

0, 0, 4, 9, 16, 2, 3, 49, 64, 81, 0, 2, 44, 69, 96, 22, 25, 289, 324, 36, 40, 44, 484, 59, 576, 6, 76, 9, 74, 841, 90, 96, 104, 1089, 1156, 122, 129, 169, 1444, 1521, 160, 681, 176, 189, 1936, 202, 211, 2209, 230, 201, 20, 260, 704, 2809, 2916, 302, 313
Offset: 0

Views

Author

Reinhard Zumkeller, Jun 07 2015

Keywords

Comments

a(A029783(n)) = A029783(n)^2; a(A189056(n)) < A189056(n)^2;
a(A178501(n)) = 0.

Examples

			.    n   n^2 |  a(n)
. -----------+------
.   20   400 |    40
.   21   441 |    44
.   22   484 |   484
.   23   529 |    59
.   24   576 |   576
.   25   625 |     6
.   26   676 |    76  not 67, as digits of n are to be removed
.   27   729 |     9                                  from left to right
.   28   784 |    74
.   29   841 |   841
.   30   900 |    90  .
		

Crossrefs

Programs

  • Haskell
    import Data.List (delete)
    a258682 n = read ('0' : minus (show (n ^ 2)) (show n)) :: Int  where
       minus [] _  = []
       minus us [] = us
       minus (u:us) vs | elem u vs = minus us $ delete u vs
                       | otherwise = u : minus us vs
  • Mathematica
    a[n_]:=Module[{idn=IntegerDigits[n],idnn=IntegerDigits[n^2],idn1},
    idn1=DeleteCases[idn,m_/;MemberQ[Complement[idn,idnn],m]];
    Do[If[First[Position[idnn,idn1[[i]]]]!= {},idnn=Delete[idnn,First[Position[idnn,idn1[[i]]]]]],
    {i,1,Length[idn1]}];FromDigits[idnn]]//Quiet;
    a/@Range[0,56] (* Ivan N. Ianakiev, Jun 11 2015 *)

A136859 Numbers k such that k and k^2 use only the digits 0, 1, 4 and 6.

Original entry on oeis.org

0, 1, 4, 10, 40, 100, 400, 1000, 4000, 10000, 40000, 100000, 400000, 1000000, 4000000, 10000000, 40000000, 100000000, 400000000, 1000000000, 4000000000, 10000000000, 40000000000, 100000000000, 400000000000, 1000000000000, 4000000000000, 10000000000000, 40000000000000, 100000000000000, 400000000000000
Offset: 1

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Author

Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008

Keywords

Comments

Generated with DrScheme.
Are the formulas conjectured or proved? For example, the analogous sequence for {0,1,2,4} contains the sporadic solution 1010000104010000101. Clearly, if a(n) is in the sequence then 10*a(n) is also in the sequence. Is there any term that is not 0, 1, or 4 times a power of 10? - M. F. Hasler, Jan 26 2016
Answer: the formulas were merely conjectures. It appears that it is an open question as to whether there is any other type of term. - N. J. A. Sloane, Jan 29 2016
David W. Wilson has observed that the real number n = 2/3 = 0.66666... with n^2 = 4/9 = 0.44444... (almost) satisfies the requirement of this sequence. - N. J. A. Sloane, Jan 30 2016

Examples

			400000000000000^2 = 160000000000000000000000000000.
		

Crossrefs

Programs

  • Mathematica
    clearQ[n_]:=Module[{dc = DigitCount[n]}, dc[[2]] == dc[[3]] == dc[[5]] == dc[[7]] == dc[[8]] == dc[[9]] == 0]
    Select[Range[0, 2*10^6], clearQ[#]&&clearQ[#^2] &] (* Vincenzo Librandi, Feb 02 2016 *)

Formula

Conjectures from Philippe Deléham, Mar 11 2014: (Start)
G.f.: x^2*(1+4*x)/(1-10*x^2);
a(1) = 0, a(2) = 1, a(3) = 4, a(n) = 10*a(n-2) for n>3. (End)
This yields: a(n) = 4^(n mod 2)*A178501(floor(n/2)), where A178501(n) = floor(10^(k-1)). - M. F. Hasler, Nov 09 2017

Extensions

Replaced formulas by conjectures, deleted b-file and computer program based on these conjectures. - N. J. A. Sloane, Jan 29 2016
M. F. Hasler, Jan 29 2016, reports that he has confirmed that the terms shown are complete up to a(31) = 400000000000000. - N. J. A. Sloane, Jan 30 2016
Extended b-file with complete values up to a(61). - David W. Wilson, Feb 01 2016

A257085 Numbers n such that the decimal expansions of both n and n^2 only use the digits 0..6.

Original entry on oeis.org

0, 1, 2, 4, 5, 6, 10, 11, 12, 15, 16, 20, 21, 25, 32, 34, 35, 40, 45, 46, 50, 51, 55, 56, 60, 65, 66, 100, 101, 102, 105, 106, 110, 111, 112, 115, 116, 120, 121, 125, 142, 145, 146, 150, 152, 155, 156, 160, 162, 200, 201, 204, 205, 206, 210, 211, 215, 216, 225, 231, 235, 245, 246, 250, 251, 252, 254, 255, 256
Offset: 1

Views

Author

Danny Rorabaugh, Apr 15 2015

Keywords

Examples

			116 is in the list because 116 and 116^2 = 13456 do not use the digits 7, 8 or 9.
182 is not in the list because it uses the digit 8 (even though 182^2 = 33124 would be fine).
253 is not in the list because 253^2 = 6409 uses the digit 9.
		

Crossrefs

Cf. A178501 (0..1), A136808(0..2), A136809(0..3), A136810 (0..4), A257086 (0..5).

Programs

  • Mathematica
    Select[Range@ 256, Total@ Take[DigitCount[#], {7, 9}] == 0 && Total@ Take[DigitCount[#^2], {7, 9}] == 0 &] (* Michael De Vlieger, Apr 17 2015 *)
  • PARI
    isok(n) = ((vecmax(digits(n)) <= 6) && (vecmax(digits(n^2)) <= 6)) || (n==0); \\ Michel Marcus, Feb 02 2016

A257086 Numbers n such that the decimal expansions of both n and n^2 only use the digits 0..5.

Original entry on oeis.org

0, 1, 2, 5, 10, 11, 12, 15, 20, 21, 32, 35, 45, 50, 55, 100, 101, 102, 105, 110, 111, 112, 115, 120, 145, 150, 152, 155, 200, 201, 205, 210, 211, 235, 320, 321, 332, 335, 350, 351, 450, 451, 452, 500, 501, 502, 505, 550, 1000, 1001, 1002, 1005, 1010, 1011, 1012, 1015, 1020, 1021, 1050, 1055, 1100
Offset: 1

Views

Author

Danny Rorabaugh, Apr 15 2015

Keywords

Examples

			115 is in the list because 115 and 115^2 = 13225 do not use the digits 6, 7, 8, or 9.
121 is not in the list because 121^2 = 14641 uses the digit 6.
149 is not in the list because it uses the digit 9 (even though 149^2 = 22201 would be okay).
		

Crossrefs

Cf. A178501 (0..1), A136808(0..2), A136809(0..3), A136810 (0..4), A257085 (0..6).

Programs

  • Mathematica
    Select[Range@ 1100, Total@ Take[DigitCount[#], {6, 9}] == 0 && Total@ Take[DigitCount[#^2], {6, 9}] == 0 &] (* Michael De Vlieger, Apr 17 2015 *)

A305706 a(n) = smallest m such that the sum of digits of n^m is greater than n, or 0 if no such m exists.

Original entry on oeis.org

0, 0, 2, 2, 2, 2, 2, 2, 2, 3, 0, 4, 3, 2, 2, 3, 3, 2, 4, 3, 14, 4, 5, 4, 4, 5, 4, 5, 6, 6, 14, 5, 6, 5, 6, 6, 6, 5, 5, 6, 14, 7, 6, 8, 6, 7, 6, 8, 7, 7, 16, 6, 6, 8, 7, 8, 7, 7, 9, 7, 15, 8, 8, 7, 8, 8, 9, 8, 8, 8, 18, 12, 9, 9, 8, 9, 9, 9, 9, 9, 18, 10, 11, 11, 10, 11, 11, 10, 9, 10, 17, 11, 11, 10, 11, 10, 12, 12, 10, 11, 0
Offset: 0

Views

Author

Max Alekseyev, Jun 08 2018

Keywords

Comments

a(n) = smallest m such that A007953(n^m) > n, or 0 if no such m exists.
If n is a term of A178501, then a(n) = 0. - Felix Fröhlich, Jun 10 2018

Crossrefs

Programs

  • PARI
    a(n) = if(sumdigits(n) < 2, return(0), my(m=2); while(1, if(sumdigits(n^m) > n, return(m)); m++)) \\ Felix Fröhlich, Jun 10 2018
Showing 1-8 of 8 results.