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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A273907 Numbers k such that 2*10^k - 87 is prime.

Original entry on oeis.org

2, 3, 4, 9, 10, 13, 15, 24, 26, 38, 39, 42, 433, 489, 495, 513, 597, 829, 2019, 2738, 3096, 3691, 5437, 7537, 8536, 34125, 40105, 41790, 52713, 104811, 173809, 175860
Offset: 1

Views

Author

Robert Price, Jun 03 2016

Keywords

Comments

For k > 1, numbers k such that the digit 1 followed by k-2 occurrences of the digit 9 followed by the digits 13 is prime (see Example section).
a(33) > 2*10^5.

Examples

			3 is in this sequence because 2*10^3 - 87 = 1913 is prime.
Initial terms and associated primes:
a(1) = 2, 113;
a(2) = 3, 1913;
a(3) = 4, 19913;
a(4) = 9, 1999999913;
a(5) = 10, 19999999913, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[2*10^# - 87] &]
  • PARI
    is(n)=ispseudoprime(2*10^n - 87) \\ Charles R Greathouse IV, Jun 08 2016

Extensions

a(30)-a(32) from Robert Price, Apr 13 2018

A273924 Numbers k such that (7*10^k - 13)/3 is prime.

Original entry on oeis.org

1, 2, 5, 6, 28, 53, 56, 86, 88, 90, 96, 136, 142, 186, 202, 373, 448, 785, 988, 1263, 1966, 3561, 4768, 9658, 9831, 17797, 42286, 49893, 98007, 129472, 146860
Offset: 1

Views

Author

Robert Price, Jun 04 2016

Keywords

Comments

For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 3 followed by the digits 29 is prime (see Example section).
a(32) > 2*10^5.

Examples

			5 is in this sequence because (7*10^5 - 13)/3 = 233329 is prime.
Initial terms and associated primes:
a(1) = 1, 19;
a(2) = 2, 229;
a(3) = 5, 233329;
a(4) = 6, 2333329;
a(5) = 28, 23333333333333333333333333329, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[(7*10^# - 13)/3] &]
  • PARI
    is(n)=ispseudoprime((7*10^n - 13)/3) \\ Charles R Greathouse IV, Jun 08 2016

Extensions

a(30)-a(31) from Robert Price, Jul 13 2018

A273944 Numbers k such that (266*10^k - 17)/3 is prime.

Original entry on oeis.org

0, 1, 2, 3, 7, 8, 11, 14, 24, 29, 50, 78, 99, 192, 226, 519, 613, 651, 1492, 3720, 6567, 6791, 7226, 8471, 9050, 13521, 14255, 33529, 44072, 47844, 64102, 112930, 116024, 122872, 138328, 140681, 268407
Offset: 1

Views

Author

Robert Price, Jun 17 2016

Keywords

Comments

For k > 1, numbers k such that the digits 88 followed by k-1 occurrences of the digit 6 followed by the digit 1 is prime (see Example section).
a(38) > 3*10^5.

Examples

			3 is in this sequence because (266*10^3-17)/3 = 88661 is prime.
Initial terms and associated primes:
a(1) = 0, 83;
a(2) = 1, 881;
a(3) = 2, 8861;
a(4) = 3, 88661;
a(5) = 7, 886666661, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[(266*10^# - 17)/3] &]
  • PARI
    isok(n) = isprime((266*10^n - 17)/3); \\ Michel Marcus, Jun 18 2016

Extensions

a(32)-a(36) from Robert Price, Jul 16 2020
a(37) from Robert Price, Jun 21 2023

A274037 Numbers k such that 3*10^k - 49 is prime.

Original entry on oeis.org

2, 5, 6, 10, 16, 29, 35, 82, 107, 170, 185, 204, 223, 226, 388, 512, 1586, 2137, 3182, 7325, 7346, 8143, 8746, 11322, 11497, 13279, 44681, 108624, 183872
Offset: 1

Views

Author

Robert Price, Jun 07 2016

Keywords

Comments

For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 9 followed by the digits 51 is prime (see Example section).
a(31) > 2*10^5.

Examples

			5 is in this sequence because 3*10^5-49 = 299951 is prime.
Initial terms and associated primes:
a(1) = 2, 251;
a(2) = 5, 299951;
a(3) = 6, 2999951;
a(4) = 10, 29999999951;
a(5) = 16, 29999999999999951, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[3*10^# - 49] &]
  • PARI
    is(n)=ispseudoprime(3*10^n - 49) \\ Charles R Greathouse IV, Jun 08 2016

Extensions

a(28)-a(29) from Robert Price, Jul 29 2018

A274214 Numbers k such that 4*10^k + 63 is prime.

Original entry on oeis.org

0, 1, 2, 4, 6, 9, 11, 14, 16, 26, 54, 74, 111, 130, 152, 253, 345, 607, 686, 1590, 2711, 5462, 7021, 8681, 11044, 18132, 24072, 25211, 44332, 52792, 85881
Offset: 1

Views

Author

Robert Price, Jun 13 2016

Keywords

Comments

For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 0 followed by the digits 63 is prime (see Example section).
a(32) > 2*10^5.

Examples

			4 is in this sequence because 4*10^4 + 63 = 40063 is prime.
Initial terms and associated primes:
a(1) = 0, 67;
a(2) = 1, 103;
a(3) = 2, 463;
a(4) = 4, 40063;
a(5) = 6, 4000063, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[4*10^# + 63] &]
  • PARI
    is(n)=ispseudoprime(4*10^n + 63) \\ Charles R Greathouse IV, Jun 13 2017

A274238 Numbers k such that (26*10^k - 119)/3 is prime.

Original entry on oeis.org

1, 2, 3, 4, 6, 22, 25, 29, 59, 89, 221, 453, 535, 1708, 2242, 2413, 3581, 4234, 4848, 5380, 6548, 8654, 11035, 17308, 27634, 28807, 35481, 79678, 80875, 114658, 230394
Offset: 1

Views

Author

Robert Price, Jul 06 2016

Keywords

Comments

For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 6 followed by the digits 27 is prime (see Example section).
a(32) > 3*10^5.

Examples

			3 is in this sequence because (26*10^3 - 119)/3 = 8627 is prime.
Initial terms and associated primes:
a(1) = 1, 47;
a(2) = 2, 827;
a(3) = 3, 8627;
a(4) = 4, 86627;
a(5) = 6, 8666627, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Magma
    [n: n in [1..500] |IsPrime((26*10^n-119) div 3)]; // Vincenzo Librandi, Jul 07 2016
  • Mathematica
    Select[Range[0, 100000], PrimeQ[(26*10^# - 119)/3] &]
  • PARI
    lista(nn) = for(n=1, nn, if(ispseudoprime((26*10^n-119)/3), print1(n, ", "))); \\ Altug Alkan, Jul 08 2016

Extensions

a(30)-a(31) from Robert Price, Jul 12 2023

A274331 Numbers k such that (148*10^k - 1)/3 is prime.

Original entry on oeis.org

2, 3, 4, 5, 9, 27, 35, 44, 88, 104, 205, 290, 302, 381, 400, 686, 917, 1150, 2278, 2757, 3220, 3316, 7469, 9535, 21442, 46409, 103718, 123688, 147139
Offset: 1

Views

Author

Robert Price, Jun 18 2016

Keywords

Comments

Numbers k such that the digits 49 followed by k occurrences of the digit 3 is prime (see Example section).
a(30) > 2*10^5.

Examples

			3 is in this sequence because (148*10^3-1)/3 = 233329 is prime.
Initial terms and associated primes:
a(1) = 2, 4933;
a(2) = 3, 49333;
a(3) = 4, 493333;
a(4) = 5, 4933333;
a(5) = 9, 49333333333, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[(148*10^# - 1)/3] &]
  • PARI
    is(n)=ispseudoprime((148*10^n - 1)/3) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(27)-a(29) from Robert Price, Mar 18 2020

A274336 Numbers k such that (16*10^k - 91)/3 is prime.

Original entry on oeis.org

1, 2, 3, 5, 16, 18, 22, 31, 40, 98, 99, 192, 233, 367, 501, 1102, 1381, 1416, 2018, 6156, 6860, 7377, 14004, 16634, 21422, 27654, 85473, 260256, 265052, 274251
Offset: 1

Views

Author

Robert Price, Jun 22 2016

Keywords

Comments

For k > 1, numbers k such that the digit 5 followed by k-1 occurrences of the digit 3 followed by the digits 03 is prime (see Example section).
a(31) > 3*10^5.

Examples

			3 is in this sequence because (16*10^3 - 91)/3 = 5303 is prime.
Initial terms and associated primes:
a(1) = 1, 23;
a(2) = 2, 503;
a(3) = 3, 5303;
a(4) = 5, 533303;
a(5) = 16, 53333333333333303, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[(16*10^# - 91)/3] &]
  • PARI
    is(n)=ispseudoprime((16*10^n - 91)/3) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(28)-a(30) from Robert Price, Jun 01 2023

A274456 Numbers k such that 5*10^k + 77 is prime.

Original entry on oeis.org

1, 2, 3, 4, 6, 8, 19, 27, 37, 56, 66, 136, 148, 387, 534, 536, 1273, 1593, 1796, 2026, 2164, 2502, 6128, 18714, 23327, 25427, 46461, 88182, 88377, 104326, 127153, 135019
Offset: 1

Views

Author

Robert Price, Jun 23 2016

Keywords

Comments

For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 0 followed by the digits 77 is prime (see Example section).
a(33) > 2*10^5.

Examples

			3 is in this sequence because 5*10^3 + 77 = 5077 is prime.
Initial terms and associated primes:
a(1) = 1, 127;
a(2) = 2, 577;
a(3) = 3, 5077;
a(4) = 4, 50077;
a(5) = 6, 5000077, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[5*10^# + 77] &]
  • PARI
    is(n)=ispseudoprime(5*10^n + 77) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(30)-a(32) from Robert Price, Dec 30 2018

A274911 Numbers k such that 7*10^k + 87 is prime.

Original entry on oeis.org

1, 2, 5, 6, 18, 23, 59, 86, 115, 119, 251, 365, 370, 447, 1672, 3076, 3973, 5611, 7687, 8824, 13026, 17141, 17971, 23346, 29138, 94373, 94563, 142189, 156956, 255167, 266731
Offset: 1

Views

Author

Robert Price, Nov 11 2016

Keywords

Comments

For k > 1, numbers k such that the digit 7 followed by k-2 occurrences of the digit 0 followed by the digits 87 is prime (see Example section).
a(32) > 3*10^5.

Examples

			5 is in this sequence because 7*10^5 + 87 = 700087 is prime.
Initial terms and associated primes:
a(1) = 1, 157;
a(2) = 2, 787;
a(3) = 5, 700087;
a(4) = 6, 7000087;
a(5) = 18, 7000000000000000087, etc.

Links

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

  • Mathematica
    Select[Range[0, 100000], PrimeQ[7*10^# + 87] &]
  • PARI
    is(n)=ispseudoprime(7*10^n + 87) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(28)-a(29) from Robert Price, Jul 27 2019
a(30)-a(31) from Robert Price, May 31 2023
Previous Showing 71-80 of 498 results. Next

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

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