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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A178960 Numbers n such that n! contains every digit at least once.

Original entry on oeis.org

23, 27, 31, 33, 34, 35, 36, 37, 39, 40, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101
Offset: 1

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Author

Michel Lagneau, Dec 31 2010

Keywords

Examples

			23 is in the sequence because 23! = 25852016738884976640000 contains every
  digit at least once.
		

Crossrefs

Programs

  • Magma
    [n: n in [0..101] | Seqset(Intseq(Factorial(n))) eq {0..9}]; // Bruno Berselli, May 17 2011
  • Maple
    with(numtheory):Digits:=200:B:={0,1,2,3,4,5,6,7,8,9}: T:=array(1..250) : for
      p from 1 to 200 do:ind:=0:n:=p!:l:=length(n):n0:=n:s:=0:for m from 1 to l do:q:=n0:u:=irem(q,10):v:=iquo(q,10):n0:=v : T[m]:=u:od: A:=convert(T,set):z:=nops(A):if A intersect B = B and ind=0 then ind:=1: printf(`%d, `,p):else fi:od:
  • Mathematica
    Select[Range[101], Length[Union[IntegerDigits[#!]]] == 10 &]

A261213 Odd numbers n such that n^2 = m + (m+1), where both m and m+1 have no repeated digits.

Original entry on oeis.org

1, 3, 5, 7, 9, 11, 13, 23, 27, 29, 31, 35, 37, 39, 41, 43, 57, 63, 69, 77, 81, 87, 89, 95, 109, 113, 121, 125, 127, 129, 137, 163, 193, 219, 239, 271, 273, 279, 281, 285, 305, 311, 315, 331, 339, 353, 357, 377, 381, 395, 403, 409, 435, 441, 443, 597
Offset: 1

Views

Author

Pieter Post, Aug 12 2015

Keywords

Comments

This sequence is finite and a(146) = 40797 is the last term. 40797^2 = 1664395209 and 1664395209 = 832197604 + 832197605. These last two numbers both have no repeating digits.

Examples

			5 is in the sequence, because 5^2 = 25. 25 = 12 + 13. 12 and 13 both have no repeating digits.
		

Crossrefs

Programs

  • Mathematica
    nr[n_] := 1 == Max@ DigitCount@ n; Select[ Range[1, 10^5, 2], nr[x= Floor[#^2 / 2]] && nr[x + 1] &] (* Giovanni Resta, Aug 12 2015 *)

A363909 Numbers whose square and cube taken together contain each decimal digit at least twice.

Original entry on oeis.org

6534, 11027, 11994, 21906, 22178, 22195, 23317, 24567, 27019, 27963, 28354, 29099, 29309, 29339, 29375, 29558, 29621, 30184, 30552, 30584, 31578, 31727, 32447, 32633, 32793, 32912, 32923, 33087, 33257, 33527, 34284, 35717, 36943, 36958, 37697, 38463
Offset: 1

Views

Author

M. F. Hasler, Jun 27 2023

Keywords

Comments

The first term, a(1) = 6534 is the only number of which the square and cube taken together contain each digit 0 to 9 exactly twice.
Presumably a(n) ~ A363905(n) ~ n. - Charles R Greathouse IV, Jul 03 2023

Examples

			6534^2 = 42693156, 6534^3 = 278957081304, which together contain each digit 0-9 exactly twice.
		

Crossrefs

Cf. A363905: square and cube together contain each digit at least once.
Cf. A036744, A054038, A071519 and A156977 for "pandigital" squares.
Cf. A119735: Numbers n such that every digit occurs at least once in n^3.

Programs

  • PARI
    is(n)=#Set(n=concat(digits(n^2),digits(n^3)))>9&&(n=vecsort(n))[#n-1]==9&&!n[2]&&!for(i=3,#n-2,n[i]>n[i-1]&&n[i]
    				

A198863 Numbers whose squares are pandigital numbers with exactly two occurrences of each digit.

Original entry on oeis.org

3164252736, 3164326683, 3164389113, 3164391957, 3164406057, 3164416923, 3164421333, 3164454864, 3164466768, 3164482974, 3164528124, 3164547114, 3164689392, 3164695206, 3164735277, 3164770866, 3164789766, 3164863185, 3164867118, 3164907357, 3165009693
Offset: 1

Views

Author

Pablo Martínez, Oct 30 2011

Keywords

Comments

Later terms include: 4000171725, 4000183233, 4000198443, 4000203567.
Because the sum of the digits of a(n)^2 is 90, 9 divides a(n)^2. Hence, 3 divides a(n). - T. D. Noe, Nov 08 2011

Examples

			4000171725^2 = 16001373829489475625.
		

Crossrefs

Cf. A156977 (n^2 contains each digit once).

Programs

  • Mathematica
    Select[Range[3164250000, 3164450000], Union[DigitCount[#^2]] == {2} &] (* Alonso del Arte, Oct 31 2011 *)
    t = {}; n = 3164211348; nMax = 9994386752; While[n <= nMax && Length[t] < 21, While[n <= nMax && Union[DigitCount[n^2]] != {2}, n = n + 3]; If[n <= nMax, AppendTo[t, n]; Print[n]; n = n + 3]]; t (* T. D. Noe, Nov 08 2011 *)

Extensions

All displayed terms are from Charles R Greathouse IV, Alonso del Arte and T. D. Noe, Nov 08 2011
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