A168447 - OEIS

%I #10 Sep 08 2022 08:45:49

%S 13,17,19,23,31,43,47,67,71,79,83,103,107,139,179,191,223,227,251,263,

%T 283,359,367,431,439,443,479,499,503,587,607,619,643,647,659,683,787,

%U 823,827,839,907,911,947,983,1039,1087,1091,1151,1163,1187,1367,1399

%N Primes p such that floor(p/6) is also prime.

%H Vincenzo Librandi, <a href="/A168447/b168447.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) >> n log^2 n. - _Charles R Greathouse IV_, Feb 23 2017

%t Select[Prime[Range[6! ]],PrimeQ[Floor[ #/6]]&]

%o (Magma) [p: p in PrimesUpTo(1400) | IsPrime(Floor(p/6))]; // _Vincenzo Librandi_, Apr 16 2013

%o (PARI) is(n)=isprime(n) && isprime(n\6) \\ _Charles R Greathouse IV_, Feb 23 2017

%Y Cf. A075519, A168446.

%K nonn,easy

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Nov 25 2009

%E Definition corrected by _R. J. Mathar_, Dec 06 2009