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.

A248349 Numbers k such that 10^k + 123456789 is prime.

Original entry on oeis.org

4, 11, 17, 23, 26, 79, 82, 221, 526, 821, 1204, 5392, 13139, 35879, 60991, 77669
Offset: 1

Views

Author

Derek Orr, Oct 05 2014

Keywords

Comments

a(14) > 20000.
a(17) > 2*10^5. - Robert Price, Oct 26 2019

Crossrefs

Cf. A248350, A248351, A248352, A050289.

Programs

  • Magma
    [n: n in [1..500] | IsPrime(10^n + 123456789)]; // Vincenzo Librandi, Oct 12 2014
  • Mathematica
    Select[Range[10^4], PrimeQ[10^# + 123456789] &] (* Robert Price, Sep 08 2019 *)
  • PARI
    for(n=1,10^4,if(ispseudoprime(10^n + 123456789),print1(n,", ")))

Extensions

a(14)-a(16) from Robert Price, Oct 26 2019

A248350 Numbers n such that 10^n - 123456789 is prime.

Original entry on oeis.org

9, 10, 13, 19, 26, 68, 73, 115, 190, 195, 232, 549, 742, 1502, 2239, 2618, 5143, 8081, 9442, 31402, 77919, 93790, 99434, 120841
Offset: 1

Views

Author

Derek Orr, Oct 05 2014

Keywords

Comments

a(26) > 200000. - Robert Price, Jun 06 2020

Crossrefs

Cf. A248349, A248351, A248352, A050289.

Programs

  • PARI
    for(n=1,10^4,if(ispseudoprime(10^n - 123456789),print1(n,", ")))

Extensions

a(21)-a(25) from Robert Price, Feb 26 2020

A248352 Numbers k such that 10^k - 987654321 is prime.

Original entry on oeis.org

986, 1240, 1928, 4054, 14252, 47528, 101728
Offset: 1

Views

Author

Derek Orr, Oct 05 2014

Keywords

Comments

Note that 987654321 is the largest pandigital number in base-10, omitting 0.

Crossrefs

Cf. A248349, A248350, A248351, A050289.

Programs

  • Mathematica
    Select[Range[10000], PrimeQ[10^# - 987654321] &] (* Robert Price, Dec 05 2019 *)
  • PARI
    for(n=1,10^4,if(ispseudoprime(10^n-987654321),print1(n,", ")))

Extensions

a(6)-a(7) from Robert Price, Dec 05 2019

A258932 Numbers k such that 10^k + 103 is prime.

Original entry on oeis.org

1, 3, 4, 5, 7, 9, 10, 11, 27, 35, 85, 169, 209, 221, 321, 347, 603, 610, 1229, 1391, 2171, 2303, 2679, 3977, 4545, 5721, 7090, 35877
Offset: 1

Views

Author

Vincenzo Librandi, Jun 15 2015

Keywords

Comments

a(29) > 60000. - Michael S. Branicky, Apr 27 2025

Examples

			For n = 3, a(3) = 10^3 + 103 = 1103, which is prime.

Crossrefs

Sequences of the type 10^n+k: A049054 (k=3), A088274 (k=7), A088275 (k=9), A095688 (k=13), A108052 (k=19), A108050 (k=21), A108312 (k=27), A107083 (k=31), A107084 (k=33), A135109 (k=37), A135108 (k=39), A108049 (k=43), A108054 (k=49), A135118 (k=51), A135119 (k=57), A135116 (k=61), A135115 (k=63), A135113 (k=67), A135114 (k=69), A135132 (k=73), A135131 (k=79), A137848 (k=81), A135117 (k=87), A110918 (k=91), A135112 (k=93), A135107 (k=97), A110980 (k=99), this sequence (k=103), A258933 (k=109), A165508 (k=111), A248349 (k=123456789), A248351 (k=987654321).

Programs

  • Magma
    [n: n in [1..600] | IsPrime(10^n+103)];
  • Mathematica
    Select[Range[5000], PrimeQ[10^# + 103] &]
  • PARI
    is(n)=ispseudoprime(10^n+103) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(26)-a(28) from Jens Kruse Andersen, Jun 23 2015
Showing 1-4 of 4 results.

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

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