A283809 Squarefree numbers k such that 6*k - 1 and 6*k + 1 are twin primes.

1, 2, 3, 5, 7, 10, 17, 23, 30, 33, 38, 47, 58, 70, 77, 87, 95, 103, 107, 110, 137, 138, 143, 170, 177, 182, 205, 213, 215, 217, 238, 247, 278, 283, 287, 298, 313, 322, 347, 355, 357, 373, 385, 390, 397, 443, 455, 465, 467, 542, 543, 555, 562, 565, 577, 590, 593, 597, 642, 653, 655, 667, 670, 682

Offset: 1

Author

Juri-Stepan Gerasimov, Mar 17 2017

Keywords

• nonn
• easy

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A002822 and of A005117. Supersequence of A060212.

Programs

Magma

[n: n in [1..700] | IsSquarefree(n) and IsPrime(6*n-1) and IsPrime(6*n+1)];

Mathematica

Select[Range[100], SquareFreeQ[#] && PrimeQ[6# - 1] && PrimeQ[6# + 1] &] (* Indranil Ghosh, Mar 17 2017 *)

PARI

is(n)=isprime(6*n-1) && isprime(6*n+1) && issquarefree(n) \\ Charles R Greathouse IV, Mar 17 2017