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A075749
Numbers k such that 210*k +- 1 are twin primes.
2
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
1,1
LINKS
EXAMPLE
k = 2 is a term since 210*2 - 1 = 419 and 210*2 + 1 = 421 are twin primes.
MATHEMATICA
Select[Range[6! ], PrimeQ[210*#-1]&&PrimeQ[210*#+1]&] (* Vladimir Joseph Stephan Orlovsky, Apr 08 2010 *)
PROG
(PARI) isok(n) = isprime(210*n+1) && isprime(210*n-1); \\ Michel Marcus, Jan 14 2015
(Magma) [k:k in [1..320]| IsPrime(210*k-1) and IsPrime(210*k+1)]; // Marius A. Burtea, Jan 01 2020
CROSSREFS
Cf. A002822 (with 6*k +- 1), A176114 (with 30*k +- 1).
Sequence in context: A032541 A363981 A281644 * A138837 A038899 A218582
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Oct 08 2002
STATUS
approved