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.

A236685 Numbers n such that n^A062518(n) is missing more than one digit.

Original entry on oeis.org

14, 17, 43, 57, 75, 78, 93, 102, 138, 139, 149, 152, 165, 167, 176, 177, 196, 228, 248, 253, 265, 276, 289, 347, 351, 352, 357, 382, 395, 424, 430, 432, 437, 438, 449, 455, 456, 462, 477, 489, 492, 502, 511, 554, 570, 605, 634, 649, 656, 679, 682
Offset: 1

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Author

Derek Orr, Jan 29 2014

Keywords

Comments

A062518(n) is the maximum power k such that k^n does not contain all ten decimal digits.

Examples

			A062518(43) = 20. And 43^20 = 467056167777397914441056671494001 is missing an 8 and a 2. Thus, 43 is a member of this sequence.
		

Crossrefs

Cf. A062518.

Programs

  • Python
    def PanDigNum(x):
      a = '1234567890'
      lst = []
      if DigitSum(x) == 1:
        return None
      for n in range(-200,0):
        count = 0
        for i in a:
          if str(x**(-n)).count(i) > 0:
            count += 1
          else:
            lst.append(i)
        if count < len(a):
          if len(lst) > 1:
            return x
          else:
            break

A036987 Fredholm-Rueppel sequence.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 0

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Author

Keywords

Comments

Binary representation of the Kempner-Mahler number Sum_{k>=0} 1/2^(2^k) = A007404.
a(n) = (product of digits of n; n in binary notation) mod 2. This sequence is a transformation of the Thue-Morse sequence (A010060), since there exists a function f such that f(sum of digits of n) = (product of digits of n). - Ctibor O. Zizka, Feb 12 2008
a(n-1), n >= 1, the characteristic sequence for powers of 2, A000079, is the unique solution of the following formal product and formal power series identity: Product_{j>=1} (1 + a(j-1)*x^j) = 1 + Sum_{k>=1} x^k = 1/(1-x). The product is therefore Product_{l>=1} (1 + x^(2^l)). Proof. Compare coefficients of x^n and use the binary representation of n. Uniqueness follows from the recurrence relation given for the general case under A147542. - Wolfdieter Lang, Mar 05 2009
a(n) is also the number of orbits of length n for the map x -> 1-cx^2 on [-1,1] at the Feigenbaum critical value c=1.401155... . - Thomas Ward, Apr 08 2009
A054525 (Mobius transform) * A001511 = A036987 = A047999^(-1) * A001511 = the inverse of Sierpiński's gasket * the ruler sequence. - Gary W. Adamson, Oct 26 2009 [Of course this is only vaguely correct depending on how the fuzzy indexing in these formulas is made concrete. - R. J. Mathar, Jun 20 2014]
Characteristic function of A000225. - Reinhard Zumkeller, Mar 06 2012
Also parity of the Catalan numbers A000108. - Omar E. Pol, Jan 17 2012
For n >= 2, also the largest exponent k >= 0 such that n^k in binary notation does not contain both 0 and 1. Unlike for the decimal version of this sequence, A062518, where the terms are only conjectural, for this sequence the values of a(n) can be proved to be the characteristic function of A000225, as follows: n^k will contain both 0 and 1 unless n^k = 2^r-1 for some r. But this is a special case of Catalan's equation x^p = y^q-1, which was proved by Preda Mihăilescu to have no nontrivial solution except 2^3 = 3^2 - 1. - Christopher J. Smyth, Aug 22 2014
Image, under the coding a,b -> 1; c -> 0, of the fixed point, starting with a, of the morphism a -> ab, b -> cb, c -> cc. - Jeffrey Shallit, May 14 2016
Number of nonisomorphic Boolean algebras of order n+1. - Jianing Song, Jan 23 2020

Examples

			G.f. = 1 + x + x^3 + x^7 + x^15 + x^31 + x^63 + x^127 + x^255 + x^511 + ...
a(7) = 1 since 7 = 2^3 - 1, while a(10) = 0 since 10 is not of the form 2^k - 1 for any integer k.
		

Crossrefs

The first row of A073346. Occurs for first time in A073202 as row 6 (and again as row 8).
Congruent to any of the sequences A000108, A007460, A007461, A007463, A007464, A061922, A068068 reduced modulo 2. Characteristic function of A000225.
If interpreted with offset=1 instead of 0 (i.e., a(1)=1, a(2)=1, a(3)=0, a(4)=1, ...) then this is the characteristic function of 2^n (A000079) and as such occurs as the first row of A073265. Also, in that case the INVERT transform will produce A023359.
This is Guy Steele's sequence GS(1, 3), also GS(3, 1) (see A135416).
Cf. A054525, A047999. - Gary W. Adamson, Oct 26 2009

Programs

  • Haskell
    a036987 n = ibp (n+1) where
       ibp 1 = 1
       ibp n = if r > 0 then 0 else ibp n' where (n',r) = divMod n 2
    a036987_list = 1 : f [0,1] where f (x:y:xs) = y : f (x:xs ++ [x,x+y])
    -- Same list generator function as for a091090_list, cf. A091090.
    -- Reinhard Zumkeller, May 19 2015, Apr 13 2013, Mar 13 2013
    
  • Maple
    A036987:= n-> `if`(2^ilog2(n+1) = n+1, 1, 0):
    seq(A036987(n), n=0..128);
  • Mathematica
    RealDigits[ N[ Sum[1/10^(2^n), {n, 0, Infinity}], 110]][[1]]
    (* Recurrence: *)
    t[n_, 1] = 1; t[1, k_] = 1;
    t[n_, k_] := t[n, k] =
      If[n < k, If[n > 1 && k > 1, -Sum[t[k - i, n], {i, 1, n - 1}], 0],
       If[n > 1 && k > 1, Sum[t[n - i, k], {i, 1, k - 1}], 0]];
    Table[t[n, k], {k, n, n}, {n, 104}]
    (* Mats Granvik, Jun 03 2011 *)
    mb2d[n_]:=1 - Module[{n2 = IntegerDigits[n, 2]}, Max[n2] - Min[n2]]; Array[mb2d, 120, 0] (* Vincenzo Librandi, Jul 19 2019 *)
    Table[PadRight[{1},2^k,0],{k,0,7}]//Flatten (* Harvey P. Dale, Apr 23 2022 *)
  • PARI
    {a(n) =( n++) == 2^valuation(n, 2)}; /* Michael Somos, Aug 25 2003 */
    
  • PARI
    a(n) = !bitand(n, n+1); \\ Ruud H.G. van Tol, Apr 05 2023
    
  • Python
    from sympy import catalan
    def a(n): return catalan(n)%2 # Indranil Ghosh, May 25 2017
    
  • Python
    def A036987(n): return int(not(n&(n+1))) # Chai Wah Wu, Jul 06 2022

Formula

1 followed by a string of 2^k - 1 0's. Also a(n)=1 iff n = 2^m - 1.
a(n) = a(floor(n/2)) * (n mod 2) for n>0 with a(0)=1. - Reinhard Zumkeller, Aug 02 2002 [Corrected by Mikhail Kurkov, Jul 16 2019]
Sum_{n>=0} 1/10^(2^n) = 0.110100010000000100000000000000010...
1 if n=0, floor(log_2(n+1)) - floor(log_2(n)) otherwise. G.f.: (1/x) * Sum_{k>=0} x^(2^k) = Sum_{k>=0} x^(2^k-1). - Ralf Stephan, Apr 28 2003
a(n) = 1 - A043545(n). - Michael Somos, Aug 25 2003
a(n) = -Sum_{d|n+1} mu(2*d). - Benoit Cloitre, Oct 24 2003
Dirichlet g.f. for right-shifted sequence: 2^(-s)/(1-2^(-s)).
a(n) = A000108(n) mod 2 = A001405(n) mod 2. - Paul Barry, Nov 22 2004
a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n,k)*Sum_{j=0..k} binomial(k, 2^j-1). - Paul Barry, Jun 01 2006
A000523(n+1) = Sum_{k=1..n} a(k). - Mitch Harris, Jul 22 2011
a(n) = A209229(n+1). - Reinhard Zumkeller, Mar 07 2012
a(n) = Sum_{k=1..n} A191898(n,k)*cos(Pi*(n-1)*(k-1))/n; (conjecture). - Mats Granvik, Mar 04 2013
a(n) = A000035(A000108(n)). - Omar E. Pol, Aug 06 2013
a(n) = 1 iff n=2^k-1 for some k, 0 otherwise. - M. F. Hasler, Jun 20 2014
a(n) = ceiling(log_2(n+2)) - ceiling(log_2(n+1)). - Gionata Neri, Sep 06 2015
From John M. Campbell, Jul 21 2016: (Start)
a(n) = (A000168(n-1) mod 2).
a(n) = (A000531(n+1) mod 2).
a(n) = (A000699(n+1) mod 2).
a(n) = (A000891(n) mod 2).
a(n) = (A000913(n-1) mod 2), for n>1.
a(n) = (A000917(n-1) mod 2), for n>0.
a(n) = (A001142(n) mod 2).
a(n) = (A001246(n) mod 2).
a(n) = (A001246(n) mod 4).
a(n) = (A002057(n-2) mod 2), for n>1.
a(n) = (A002430(n+1) mod 2). (End)
a(n) = 2 - A043529(n). - Antti Karttunen, Nov 19 2017
a(n) = floor(1+log(n+1)/log(2)) - floor(log(2n+1)/log(2)). - Adriano Caroli, Sep 22 2019
This is also the decimal expansion of -Sum_{k>=1} mu(2*k)/(10^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

Extensions

Edited by M. F. Hasler, Jun 20 2014

A130696 Numbers k such that 2^k does not contain all ten decimal digits.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 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, 69, 71, 72, 73, 74, 75, 76, 77, 78, 80, 81, 83, 85, 86, 90, 91, 92, 93, 99, 102, 107, 108, 153, 168
Offset: 1

Views

Author

Greg Dresden, Jul 10 2007

Keywords

Comments

It is believed that 168 is the last number in this list; 2^168 is a 51-digit number that contains all the digits except (oddly enough) 2.
There are no more terms less than 10^10. - David Radcliffe, Apr 11 2019

Examples

			20 is in this list because 2^20 = 1048576, which doesn't contain all ten digits.
68 is the first number not in this list; 2^68 = 295147905179352825856 and this contains all ten digits.
		

Crossrefs

Complement of A130694.

Programs

  • Mathematica
    A2 := {}; Do[If[Length[Union[ IntegerDigits[2^ n]]] != 10, A2 = Join[A2, {n}]], {n, 1, 3000}]; Print[A2]
    Select[Range[10^6]-1,MemberQ[DigitCount[2^#],0]&] (* Hans Rudolf Widmer, Jun 23 2021 *)
  • PARI
    hasalldigits(n) = #vecsort(digits(n), , 8)==10
    is(n) = !hasalldigits(2^n) \\ Felix Fröhlich, Apr 11 2019
  • Python
    print([n for n in range(1000) if len(set(str(2**n))) < 10]) # David Radcliffe, Apr 11 2019
    

Extensions

a(1) = 0 prepended by David Radcliffe, Apr 11 2019

A090493 Least k such that n^k contains all the digits from 0 through 9, or 0 if no such k exists.

Original entry on oeis.org

0, 68, 39, 34, 19, 20, 18, 28, 24, 0, 23, 22, 22, 21, 12, 17, 14, 21, 17, 51, 17, 18, 14, 19, 11, 18, 13, 11, 12, 39, 11, 14, 16, 14, 19, 10, 13, 14, 17, 34, 11, 17, 13, 16, 15, 11, 12, 12, 9, 18, 16, 11, 13, 10, 12, 7, 13, 11, 11, 20, 14, 18, 13, 14, 10, 13, 10, 9, 11, 18, 15
Offset: 1

Views

Author

Amarnath Murthy, Dec 03 2003

Keywords

Comments

Note that the values of n for which a(n) = 1 have density 1.
Is it known that a(n)=0 only for n a power of 10? - Christopher J. Smyth, Aug 21 2014
a(n) >= ceiling(log_n(10)*9), whenever a(n)>0. This is because in order for an integer to have 10 digits its base-10 magnitude must be at least 9. - Ely Golden, Sep 06 2017

Examples

			a(5)=19: 5^19 = 19073486328125.
		

Crossrefs

Exponents of powers of k that contain all ten decimal digits: A130694 (k=2), A236673 (k=3), A284670 (k=5), A284672 (k=7).

Programs

  • Maple
    a:= proc(n) local k;
       if n = 10^ilog10(n) then return 0 fi;
       for k from 1 do
         if nops(convert(convert(n^k,base,10),set))=10 then return k fi
       od
    end proc:
    seq(a(n),n=1..100); # Robert Israel, Aug 20 2014
  • Mathematica
    Table[If[IntegerQ@ Log10[n], 0, SelectFirst[Range[#, # + 100] &@ Ceiling[9 Log[n, 10]], NoneTrue[DigitCount[n^#], # == 0 &] &]], {n, 71}] (* Michael De Vlieger, Sep 06 2017 *)
  • PARI
    a(n) = if (n == 10^valuation(n, 10), return (0)); k=1; while(#vecsort(digits(n^k),,8)!=10, k++); k; \\ Michel Marcus, Aug 20 2014
    
  • Python
    def a(n):
      s = str(n)
      if n == 1 or (s.count('0')==len(s)-1 and s.startswith('1')):
        return 0
      k = 1
      count = 0
      while count != 10:
        count = 0
        for i in range(10):
          if str(n**k).count(str(i)) == 0:
            count += 1
            break
        if count:
          k += 1
        else:
          return k
    n = 1
    while n < 100:
      print(a(n), end=', ')
      n += 1
    # Derek Orr, Aug 20 2014

Formula

a(10^e) = 0; a(m^e) = a(m)/e for e dividing a(m). - Reinhard Zumkeller, Dec 06 2004

Extensions

More terms from Reinhard Zumkeller, Dec 06 2004
Corrected a(15), a(17), a(38), a(48), a(56) and a(65). (For each of these terms, the only 1 in n^k is the first digit.) - Jon E. Schoenfield, Sep 20 2008
Showing 1-4 of 4 results.