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 1-9 of 9 results.

A051833 Primes of form (2*10^(5n) - 10^(4n) + 2*10^(3n) + 10^(2n) + 10^n + 1)/3.

Original entry on oeis.org

2, 64037, 66666663333334000000033333336666667
Offset: 1

Views

Author

G. L. Honaker, Jr., Dec 11 1999

Keywords

Comments

The Baxter-Hickerson function provides a number whose cube lacks zeros.
Next term has 665 digits and is in b-file.

Crossrefs

Programs

  • Mathematica
    Select[Table[(2*10^(5*n) - 10^(4*n) + 2*10^(3*n) + 10^(2*n) + 10^n + 1)/3, {n, 0, 150}], PrimeQ] (* Amiram Eldar, Jul 18 2025 *)

Formula

a(n) = A052427(A051832(n)). - Amiram Eldar, Jul 18 2025

A051750 Primes whose cubes lack zeros.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 41, 53, 61, 71, 83, 97, 113, 137, 139, 151, 157, 167, 173, 179, 181, 191, 197, 211, 233, 239, 241, 251, 257, 263, 277, 283, 293, 307, 331, 337, 347, 353, 359, 373, 379, 383, 389, 409, 421, 433, 457, 461, 463, 499, 503
Offset: 1

Views

Author

G. L. Honaker, Jr., Dec 07 1999

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Prime[Range[100]],FreeQ[IntegerDigits[#^3],0]&] (* Harvey P. Dale, Jan 06 2017 *)
  • PARI
    isok(n) = isprime(n) && vecmin(digits(n^3)); \\ Michel Marcus, Jan 06 2014

Extensions

More terms from Michel Marcus, Jan 06 2014

A051832 Numbers k such that (2*10^(5*k) - 10^(4*k) + 2*10^(3*k) + 10^(2*k) + 10^k + 1)/3 is prime.

Original entry on oeis.org

0, 1, 7, 133
Offset: 1

Views

Author

G. L. Honaker, Jr., Dec 11 1999

Keywords

Comments

The Baxter-Hickerson function provides a number whose cube lacks zeros.
The next term is > 4400. - Jason Earls, Sep 10 2005
The next term is > 20000 (found using pfgw64). - Patrick De Geest, Jul 22 2012

Crossrefs

Programs

  • Maple
    f := n->(2*10^(5*n) - 10^(4*n) + 2*10^(3*n) + 10^(2*n) + 10^n + 1)/3;
  • PARI
    is(n)=isprime((2*10^(5*n)-10^(4*n)+2*10^(3*n)+10^(2*n)+10^n+1)/3) \\ Charles R Greathouse IV, Feb 17 2017

A051751 Cubes arising in A051750.

Original entry on oeis.org

8, 27, 125, 343, 1331, 2197, 4913, 6859, 12167, 24389, 29791, 68921, 148877, 226981, 357911, 571787, 912673, 1442897, 2571353, 2685619, 3442951, 3869893, 4657463, 5177717, 5735339, 5929741, 6967871, 7645373, 9393931, 12649337
Offset: 1

Views

Author

G. L. Honaker, Jr., Dec 07 1999

Keywords

Crossrefs

Formula

A030078 INTERSECT A052382. - R. J. Mathar, Mar 23 2007

A052045 Cubes lacking the digit zero in their decimal expansion.

Original entry on oeis.org

1, 8, 27, 64, 125, 216, 343, 512, 729, 1331, 1728, 2197, 2744, 3375, 4913, 5832, 6859, 9261, 12167, 13824, 15625, 17576, 19683, 21952, 24389, 29791, 32768, 35937, 42875, 46656, 54872, 59319, 68921, 85184, 91125, 97336, 117649, 132651, 148877
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Comments

This sequence is infinite since A052427(n)^3 is a term for all n>=0. - Amiram Eldar, Nov 23 2020

Crossrefs

Programs

  • Maple
    select(t -> not has(convert(t,base,10),0), [seq(m^3,m=1..10^3)]); # Robert Israel, Aug 24 2014
  • Mathematica
    Select[Range[53]^3, DigitCount[#, 10, 0] == 0 &] (* Amiram Eldar, Nov 23 2020 *)
  • PARI
    lista(nn) = {for (n=1, nn, if (vecmin(digits(cub=n^3)), print1(cub, ", ")););} \\ Michel Marcus, Aug 25 2014
  • Python
    A052045 = [n**3 for n in range(1,10**5) if not str(n**3).count('0')]
    # Chai Wah Wu, Aug 24 2014
    

Formula

Intersection of A052382 and A000578; A168046(a(n))*A010057(a(n)) = 1. - Reinhard Zumkeller, Dec 01 2009
a(n) = A052044(n)^3. - Amiram Eldar, Nov 23 2020

A052427 Baxter-Hickerson numbers.

Original entry on oeis.org

2, 64037, 6634003367, 666334000333667, 66663334000033336667, 6666633334000003333366667, 666666333334000000333333666667, 66666663333334000000033333336666667
Offset: 0

Views

Author

Keywords

Comments

From Amiram Eldar, Nov 23 2020: (Start)
Named after Lew Baxter and Dean Hickerson.
Pegg (1999) conjectured that the sequence of zeroless cubes (A052045) is finite. On April 19, 1999, Hickerson gave the counterexample: if n == 2 (mod 3) and n >= 5, then the cube of (2*10^(5*n) - 10^(4*n) + 17*10^(3*n-1) + 10^(2*n) + 10^n - 2)/3 is zeroless. Three days later, Baxter gave a simpler variation which is valid for all n>=0 and is given in the Formula section. (End)

References

  • Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005. See p. 109.

Crossrefs

Subsequence of A052044.

Programs

  • Maple
    a(0) = 2, and 2^3 = 8 is zeroless.
    a(1) = 64037, and 64037^3 = 262598918898653 is zeroless.
  • Mathematica
    a[n_] := (2*10^(5*n) - 10^(4*n) + 2*10^(3*n) + 10^(2*n) + 10^n + 1)/3; Array[a, 10, 0] (* Amiram Eldar, Nov 23 2020 *)

Formula

a(n) = (2*10^(5*n) - 10^(4*n) + 2*10^(3*n) + 10^(2*n) + 10^n + 1)/3 (Baxter, 1999). - Amiram Eldar, Nov 23 2020

Extensions

Offset changed to 0 by Amiram Eldar, Nov 23 2020

A116978 Cubes whose multiplicative digital root is also a cube.

Original entry on oeis.org

0, 1, 8, 64, 125, 343, 512, 1000, 4096, 4913, 5832, 6859, 8000, 9261, 10648, 13824, 15625, 17576, 19683, 21952, 27000, 32768, 35937, 39304, 42875, 46656, 50653, 54872, 59319, 64000, 68921, 74088, 79507, 85184, 91125, 97336, 103823, 110592, 117649
Offset: 1

Views

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 01 2006

Keywords

Comments

Presumably a(n) ~ n^3. Up to 10^6 there are 14 missing cubes, up to 10^9 there are 36, up to 10^12 there are 81, up to 10^15 there are 155, up to 10^18 there are 267, up to 10^21 there are 517, and up to 10^24 there are 846. - Charles R Greathouse IV, Nov 17 2015

Crossrefs

Programs

  • Maple
    A007954 := proc(n) return mul(d, d=convert(n, base, 10)): end: A116978 := proc(n) option remember: local k,m: if(n=1)then return 0:fi: for k from procname(n-1)+1 do m:=k^3: while(length(m)>1)do m:=A007954(m): od: if(m in {0,1,8})then return k: fi: od: end: seq(A116978(n)^3, n=1..50); # Nathaniel Johnston, May 05 2011
  • Mathematica
    fQ[n_] := IntegerQ[ FixedPoint[Times @@ IntegerDigits@# &, n]^(1/3)]; Select[Range[0, 48]^3, fQ@# &] (* Robert G. Wilson v, Apr 03 2006 *)
  • PARI
    t(k)=while(k>9, k=prod(i=1, #k=digits(k), k[i])); k
    for(n=0, 200, if(ispower(t(n^3), 3), print1(n^3, ", "))); \\ Altug Alkan, Oct 22 2015

Formula

a(n) >= A052044(n)^3 for n > 3. - Charles R Greathouse IV, Nov 17 2015

Extensions

Corrected and extended by Robert G. Wilson v, Apr 03 2006

A333206 a(n) is the least decimal digit of n^3.

Original entry on oeis.org

0, 1, 8, 2, 4, 1, 1, 3, 1, 2, 0, 1, 1, 1, 2, 3, 0, 1, 2, 5, 0, 1, 0, 1, 1, 1, 1, 1, 1, 2, 0, 1, 2, 3, 0, 2, 4, 0, 2, 1, 0, 1, 0, 0, 1, 1, 3, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 2, 0, 1, 2, 2, 0, 1, 0, 0, 1, 2, 0, 0, 1, 3, 3, 2, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 6, 0, 0, 3, 3, 1, 1
Offset: 0

Views

Author

Robert Israel, Mar 12 2020

Keywords

Comments

Dean Hickerson found an infinite sequence of n such that a(n) > 0 (see Guy, sec F24). Are there infinitely many such that a(n) > 1? If not, what is the greatest n with a(n)=k for each k > 1?
Heuristically, we should expect on the order of ((10-m)^3/100)^d terms n with d digits and a(n) >= m. Since 5^3/100 > 1 > 4^3/100 we should expect infinitely many terms with a(n) >= 5 but only finitely many terms with a(n) >= 6. See A291644 for a(n) = 5. There are only two n <= 10^6 with a(n) >= 6, namely a(2) = 8 and a(92) = 6.

Examples

			The least digit of 6^3=216 is 1, so a(6)=1.
		

References

  • R. Guy, Unsolved Problems in Number Theory (Third edition), Springer 2004.

Crossrefs

Programs

  • Maple
    seq(min(convert(n^3,base,10)),n=0..200);

Formula

a(n) = A054054(n^3).

A358340 a(n) is the smallest n-digit number whose fourth power is zeroless.

Original entry on oeis.org

1, 11, 104, 1027, 10267, 102674, 1026708, 10266908, 102669076, 1026690113, 10266901031, 102669009704, 1026690096087, 10266900960914, 102669009608176, 1026690096080369, 10266900960803447, 102669009608034434, 1026690096080341627, 10266900960803409734, 102669009608034097731, 1026690096080340972491
Offset: 1

Views

Author

Mohammed Yaseen, Nov 10 2022

Keywords

Comments

It has been proved that there exist infinitely many zeroless squares and cubes but there is apparently no proof for 4th powers, 5th powers, etc.
This sequence approaches the decimal expansion of 9000^(-1/4). Similar sequences of other small powers k seem to approach the decimal expansion of (9*10^(k-1))^(-1/k).

Crossrefs

Programs

  • PARI
    a(n) = my(x=10^(n-1)); while(! vecmin(digits(x^4)), x++); x; \\ Michel Marcus, Nov 10 2022
    
  • PARI
    a(n) = { my(s = sqrtnint(10^(4*n - 3) \ 9, 4)); for(i = s, oo, c = i^4; if(vecmin(digits(c)) > 0, return(i) ) ) } \\ David A. Corneth, Nov 10 2022
  • Python
    from itertools import count
    from sympy import integer_nthroot
    def a(n):
        start = integer_nthroot(int("1"*(4*(n-1)+1)), 4)[0]
        return next(i for i in count(start) if "0" not in str(i**4))
    print([a(n) for n in range(1, 22)]) # Michael S. Branicky, Nov 10 2022
    

Formula

a(n) ~ 10^(n + 1/4) / sqrt(3).

Extensions

More terms from David A. Corneth, Nov 10 2022
Showing 1-9 of 9 results.