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.

A242177 Numbers k such that k*7^k + 1 is prime.

Original entry on oeis.org

34, 1980, 9898
Offset: 1

Views

Author

Vincenzo Librandi, May 08 2014

Keywords

Links

Crossrefs

Cf. similar sequences listed in A242176.

Programs

  • Magma
    [n: n in [0..3500] | IsPrime(n*7^n+1)];
  • Mathematica
    Select[Range[3500], PrimeQ[# 7^# + 1] &]
  • PARI
    is(n)=ispseudoprime(n*7^n+1) \\ Charles R Greathouse IV, May 22 2017

Extensions

a(3) from Loeh's list (see Links) - Bruno Berselli, May 08 2014

A242178 Numbers k such that k*8^k + 1 is prime.

Original entry on oeis.org

5, 17, 23, 1911, 20855, 35945, 42816
Offset: 1

Views

Author

Vincenzo Librandi, May 08 2014

Keywords

Links

Crossrefs

Cf. similar sequences listed in A242176.

Programs

  • Magma
    [n: n in [0..2000] | IsPrime(n*8^n+1)];
  • Mathematica
    Select[Range[2000], PrimeQ[# 8^# + 1] &]
  • PARI
    is(n)=ispseudoprime(n*8^n+1) \\ Charles R Greathouse IV, May 22 2017

Extensions

a(5)-a(7) from Loeh's list (see Links) - Bruno Berselli, May 08 2014

A242196 Numbers k such that k*12^k + 1 is prime.

Original entry on oeis.org

1, 8, 247, 3610, 4775, 19789, 187895
Offset: 1

Views

Author

Vincenzo Librandi, May 08 2014

Keywords

Links

Crossrefs

Cf. similar sequences listed in A242176.

Programs

  • Magma
    [n: n in [0..2300] | IsPrime(n*12^n+1)]
  • Mathematica
    Select[Range[2300], PrimeQ[# 12^# + 1] &]
  • PARI
    is(n)=ispseudoprime(n*12^n+1) \\ Charles R Greathouse IV, Jun 06 2017

Extensions

a(4)- a(7) from Loeh's list (see Links) - Bruno Berselli, May 08 2014

A242197 Numbers k such that k*14^k + 1 is prime.

Original entry on oeis.org

3, 5, 6, 9, 33, 45, 243, 252, 1798, 2429, 5686, 12509, 42545
Offset: 1

Views

Author

Vincenzo Librandi, May 08 2014

Keywords

Links

Crossrefs

Cf. similar sequences listed in A242176.

Programs

  • Magma
    [n: n in [0..2000] | IsPrime(n*14^n+1)];
  • Mathematica
    Select[Range[2000], PrimeQ[# 14^# + 1] &]
  • PARI
    is(n)=ispseudoprime(n*14^n+1) \\ Charles R Greathouse IV, Jun 06 2017

Extensions

a(10)-a(13) from Loeh's list (see Links) - Bruno Berselli, May 08 2014

A242198 Numbers k such that k*15^k + 1 is prime.

Original entry on oeis.org

8, 14, 44, 154, 274, 694, 17426, 59430
Offset: 1

Views

Author

Vincenzo Librandi, May 08 2014

Keywords

Links

Crossrefs

Cf. similar sequences listed in A242176.

Programs

  • Magma
    [n: n in [0..2500] | IsPrime(n*15^n+1)];
  • Mathematica
    Select[Range[2000], PrimeQ[# 15^# + 1] &]
  • PARI
    is(n)=ispseudoprime(n*15^n+1) \\ Charles R Greathouse IV, Jun 06 2017

Extensions

a(7)-a(8) from Loeh's list (see Links)

A242199 Numbers k such that k*16^k + 1 is prime.

Original entry on oeis.org

1, 3, 55, 81, 223, 1227, 3012, 3301
Offset: 1

Views

Author

Vincenzo Librandi, May 08 2014

Keywords

Links

Crossrefs

Cf. similar sequences listed in A242176.

Programs

  • Magma
    [n: n in [0..2000] | IsPrime(n*16^n+1)];
  • Mathematica
    Select[Range[2000], PrimeQ[# 16^# + 1] &]
  • PARI
    is(n)=ispseudoprime(n*16^n+1) \\ Charles R Greathouse IV, Jun 06 2017
  • Sage
    [n for n in (1..2000) if is_prime(n*16^n + 1)] # Bruno Berselli, May 09 2014

Extensions

a(7)-a(8) from Loeh's list (see Links)

A242269 Numbers n such that n*6^n+1 is semiprime.

Original entry on oeis.org

3, 5, 11, 12, 18, 20, 21, 24, 25, 35, 43, 45, 53, 58, 61, 71, 73, 75, 123, 124, 140, 147, 157, 205, 208, 233, 243, 245, 293, 301
Offset: 1

Views

Author

Vincenzo Librandi, May 10 2014

Keywords

Comments

The semiprimes of this form are: 649, 38881, 3990767617, 26121388033, 1828079220031489, 73123168801259521, 460675963447934977,...
464 is definitely in this sequence, however 436 may or may not be. - Carl Schildkraut, Aug 28 2015
A continuation in the range 302 ... 1000 would use all terms without "?" and potentially ?-marked terms corresponding to composites with unknown factorization: 436?, 464, 511?, 512, 613, 662?, 720, 730, 802?, 865?, 943. - Hugo Pfoertner, Aug 05 2019

Links

Crossrefs

Cf. similar sequences listed in A242203.
Cf. A050917, A242176.

Programs

  • Magma
    IsSemiprime:=func; [n: n in [1..435] | IsSemiprime(s) where s is n*6^n+1];
  • Mathematica
    Select[Range[435], PrimeOmega[# 6^# + 1] == 2 &]
  • PARI
    is(n)=bigomega(n*6^n+1)==2 \\ Anders Hellström, Aug 28 2015

Extensions

a(19)-a(30) from Carl Schildkraut, Aug 28 2015

A265013 Numbers n such that n*9^n + 1 is prime.

Original entry on oeis.org

2, 12382, 27608, 31330, 117852
Offset: 1

Views

Author

Tim Johannes Ohrtmann, Nov 30 2015

Keywords

Comments

All terms are even. - Robert Israel, Jan 18 2016

Crossrefs

Cf. A005849, A006552, A007646, A242176, A242177, A242178, A007647, A242196, A242197, A242198, A242199, A007648.

Programs

  • Magma
    [n: n in [0..100000] | IsPrime(n*9^n+1)];
  • Mathematica
    Select[Range[100000], PrimeQ[# 9^# + 1] &]
  • PARI
    for(n=1,100000, if(isprime(n*9^n+1), print1(n,", ")))

A338412 Numbers k such that k * 20^k + 1 is prime.

Original entry on oeis.org

3, 6207, 8076, 22356, 151456
Offset: 1

Views

Author

Tim Johannes Ohrtmann, Oct 25 2020

Keywords

Comments

a(6) > 219976.

Links

Crossrefs

Numbers k such that k * b^k + 1 is prime: A006093 (b=1), A005849 (b=2), A006552 (b=3), A007646 (b=4), A242176 (b=6), A242177 (b=7), A242178 (b=8), A265013 (b=9), A007647(b=10), A242196(b=12), A242197 (b=14), A242198 (b=15), A242199 (b=16), A007648 (b=18), this sequence (b=20).

Programs

  • Magma
    [n: n in [1..10000] |IsPrime(n*20^n+1)]
  • Mathematica
    Select[Range[1, 10000], PrimeQ[n*20^n+1] &]
  • PARI
    for(n=1, 10000, if(isprime(n*20^n+1), print1(n, ", ")))
Showing 1-9 of 9 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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