A024905 -id:A024905 - cp's OEIS frontend

A124127 Numbers k such that 17k + 1 is prime.

6, 8, 14, 18, 24, 26, 36, 38, 54, 56, 60, 66, 74, 78, 80, 84, 90, 98, 110, 116, 126, 138, 140, 150, 158, 164, 168, 180, 186, 194, 204, 210, 216, 228, 230, 236, 248, 260, 266, 270, 290, 294, 300, 308, 318, 320, 344, 356, 360, 368, 374, 378, 384, 386, 396, 404

Offset: 1

Parthasarathy Nambi, Nov 29 2006

			If k=116 then 17*k + 1 = 1973 (prime).

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Cf. A024905, A129484 (resulting primes).

[n: n in [0..500] | IsPrime(17*n + 1)] // Vincenzo Librandi, Mar 26 2010

Select[Range[500],PrimeQ[17#+1]&] (* Harvey P. Dale, Nov 28 2019 *)

is(n)=isprime(17*n+1) \\ Charles R Greathouse IV, Jun 13 2017

A124198 Numbers k such that 21*k + 1 is prime.

Original entry on oeis.org

2, 6, 10, 16, 18, 20, 22, 26, 30, 32, 36, 42, 46, 48, 50, 52, 62, 68, 70, 76, 82, 92, 96, 102, 108, 110, 116, 120, 126, 128, 130, 136, 146, 148, 158, 160, 168, 170, 172, 176, 178, 182, 186, 198, 200, 202, 206, 220, 222, 228, 230, 236, 238, 246, 248, 258, 262, 278

Offset: 1

Parthasarathy Nambi, Dec 06 2006

			If k=148 then 21*k + 1 = 3109 (prime).

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A024905, A124127.

[n: n in [0..300] | IsPrime(21*n + 1)] // Vincenzo Librandi, Mar 26 2010

Select[Range[300],PrimeQ[21#+1]&] (* Harvey P. Dale, Mar 08 2016 *)

is(n)=isprime(21*n+1) \\ Charles R Greathouse IV, Jun 06 2017

A111249 Numbers n such that 7*n + 8 is prime.

Original entry on oeis.org

3, 5, 9, 15, 17, 27, 29, 33, 39, 47, 53, 59, 63, 65, 69, 77, 87, 89, 93, 95, 99, 105, 107, 117, 125, 129, 135, 137, 143, 149, 155, 165, 183, 185, 195, 203, 209, 213, 225, 227, 237, 243, 245, 267, 275, 285, 287, 297, 303, 305, 315, 323, 327, 329, 333, 339, 345

Offset: 1

Parthasarathy Nambi, Oct 31 2005

nonn

One less than the associated entry in A024905.

			If n=125 then 7*n + 8 = 883 (prime).

Cf. A024900, A024902, A024905, A105772.

[n: n in [0..100000] | IsPrime(7*n+8)] // Vincenzo Librandi, Nov 13 2010

A111249:=n->`if`(isprime(7*n+8), n, NULL): seq(A111249(n), n=1..10^3); # Wesley Ivan Hurt, Feb 13 2017

Select[Range[1,351,2], PrimeQ[7#+8]&] (* Harvey P. Dale, Sep 11 2016 *)

is(n)=isprime(7*n+8) \\ Charles R Greathouse IV, Feb 14 2017

A368203 Least k such that 7nk+1 is a prime.

Original entry on oeis.org

4, 2, 2, 1, 2, 1, 4, 2, 2, 1, 6, 4, 6, 2, 2, 1, 2, 1, 12, 2, 6, 3, 6, 2, 4, 3, 2, 1, 12, 1, 6, 2, 2, 1, 2, 3, 10, 6, 2, 1, 6, 3, 10, 2, 2, 3, 2, 1, 4, 2, 4, 3, 2, 1, 6, 8, 4, 6, 2, 1, 4, 3, 2, 1, 2, 1, 4, 2, 2, 1, 14, 2, 6, 5, 2, 3, 12, 1, 4, 5, 4, 3, 2, 6

Offset: 1

Robert Price, Dec 16 2023

nonn

Robert Price, Table of n, a(n) for n = 1..5000

Cf. A016014, A024905.

A070851 lists the corresponding primes.

A368203 = {};
Do[k=1; While[!PrimeQ[7 n k+1], k++]; AppendTo[A368203,k], {n,84}];
A368203

a(n) = my(k=1); while (!isprime(7*n*k+1), k++); k; \\ Michel Marcus, Dec 16 2023

cp's OEIS Frontend

A124127 Numbers k such that 17k + 1 is prime.

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A124198 Numbers k such that 21*k + 1 is prime.

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A111249 Numbers n such that 7*n + 8 is prime.

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A368203 Least k such that 7*n*k+1 is a prime.

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A368203 Least k such that 7nk+1 is a prime.