A075749 Numbers k such that 210*k +- 1 are twin primes.

2, 5, 11, 13, 16, 28, 29, 30, 35, 36, 42, 44, 50, 51, 55, 57, 73, 86, 104, 121, 125, 128, 135, 140, 147, 148, 157, 158, 160, 161, 165, 168, 179, 193, 204, 205, 209, 223, 244, 247, 249, 251, 255, 264, 271, 273, 277, 281, 282, 290, 302, 304, 310, 312, 313, 316

Offset: 1

Author

Zak Seidov, Oct 08 2002

Keywords

• easy
• nonn

Examples

			k = 2 is a term since 210*2 - 1 = 419 and 210*2 + 1 = 421 are twin primes.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002822 (with 6*k +- 1), A176114 (with 30*k +- 1).

Programs

Magma

[k:k in [1..320]| IsPrime(210*k-1) and IsPrime(210*k+1)]; // Marius A. Burtea, Jan 01 2020

Mathematica

Select[Range[6! ],PrimeQ[210*#-1]&&PrimeQ[210*#+1]&] (* Vladimir Joseph Stephan Orlovsky, Apr 08 2010 *)

PARI

isok(n) = isprime(210*n+1) && isprime(210*n-1); \\ Michel Marcus, Jan 14 2015