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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A062586 Numbers k such that 20^k - 19^k is prime.

Original entry on oeis.org

5, 17, 109, 1979, 6899, 7331, 18661, 79621, 81649
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms k > 1000 may correspond to (unproven) strong pseudoprimes.

Links

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Extensions

a(7)-a(9) found by Jean-Louis Charton in February and March 2011
Edited by M. F. Hasler, Sep 16 2013

A062588 Numbers k such that 22^k - 21^k is prime.

Original entry on oeis.org

2, 127, 877
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

All terms are prime.
No other terms less than 10^5. - Robert Price, May 28 2012

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

A062593 Numbers k such that 27^k - 26^k is prime.

Original entry on oeis.org

2, 13, 157, 43117
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms > 1000 are often only strong pseudoprimes.
a(5) > 10^5. - Robert Price, Aug 12 2012.

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Extensions

a(4) from Robert Price, Aug 12 2012

A062604 Numbers k such that 38^k - 37^k is prime.

Original entry on oeis.org

3, 379, 383, 1373, 1609, 24611, 38281
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms greater than 1000 are often only strong pseudoprimes.
a(8) > 10^5. - Robert Price, Sep 03 2012

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Extensions

a(6) and a(7) from Robert Price, Sep 03 2012

A062608 Numbers k such that 42^k - 41^k is prime.

Original entry on oeis.org

2, 3, 5, 47, 67, 103
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms greater than 1000 are often only strong pseudoprimes.
No further terms up to 5000. - Harvey P. Dale, Mar 13 2011
a(7) > 10^5. - Robert Price, Sep 21 2012

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

A062612 Numbers k such that 46^k - 45^k is prime.

Original entry on oeis.org

3, 1087, 1879, 4349, 16829, 59791
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms greater than 1000 are often only strong pseudoprimes.
a(7)>10^5. - Robert Price, Feb 18 2013

Links

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Extensions

a(5) from Jean-Louis Charton, Jan 11 2013
a(6) from Jean-Louis Charton, Jan 16 2013

A062647 Numbers k such that 81^k - 80^k is prime.

Original entry on oeis.org

3, 43, 113, 157, 269, 709, 1109, 2027, 8297, 86837, 310721
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms greater than 1000 are often only strong pseudoprimes.
a(11) > 10^5. - Robert Price, Jan 13 2015
Factors of these numbers are of the form p = 2*n*k + 1, just like the repunit numbers, but the PRP tests are significantly slower since there is not a fast mod() property like the repunits, where (number mod Rn) can be calculated with a folding of the digits at length n in base b. However, numbers of this form b^p - (b-1)^p seem to be prime with greater relative frequency than the repunits. While the repunits have a linear fit coefficient that approaches 0.56145948 (see link below for a Generalized Repunit Conjecture), this sequence currently has a linear fit coefficient of 0.22559. - Paul Bourdelais, Jul 06 2023

Links

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Extensions

a(10) from Robert Price, Jan 13 2015 (Computer run by Adam Marciniec)
a(11) from Paul Bourdelais, Jul 06 2023

A062652 Numbers k such that 86^k - 85^k is prime.

Original entry on oeis.org

5, 11, 103, 227, 1637, 9677, 41597
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms greater than 1000 are often only strong pseudoprimes.
All terms are prime. - Robert Price, Apr 14 2014
a(8) > 10^5. - Robert Price, Apr 14 2015

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666, A215536 (primes 87^n - 86^n).

Programs

  • Mathematica
    Select[Range[0, 300], If[PrimeQ[#], PrimeQ[86^# - 85^#]] &] (* Robert Price, Apr 14 2015 *)
  • PARI
    is(n)=ispseudoprime(86^n-85^n) \\ Charles R Greathouse IV, Jun 12 2017

Extensions

a(7) from Robert Price (computer run by Adam Marciniec), Apr 14 2015

A062655 Numbers k such that 89^k - 88^k is prime.

Original entry on oeis.org

3, 5, 997, 4253, 52511, 59221
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

Terms greater than 1000 are often only strong pseudoprimes.
a(7) > 10^5. - Robert Price, Jun 16 2015

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Extensions

a(5)-a(6) from Robert Price (computer run by Adam Marciniec), Jun 16 2015

A062665 Numbers k such that 99^k - 98^k is prime.

Original entry on oeis.org

2, 709
Offset: 1

Views

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

Comments

a(3) > 20000. - Derek Orr, Sep 03 2014
Terms must be prime. - Derek Orr, Sep 03 2014
a(3) > 10^5. - Robert Price, Mar 22 2015

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

Previous Showing 51-60 of 122 results. Next

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