A168447 Primes p such that floor(p/6) is also prime.
13, 17, 19, 23, 31, 43, 47, 67, 71, 79, 83, 103, 107, 139, 179, 191, 223, 227, 251, 263, 283, 359, 367, 431, 439, 443, 479, 499, 503, 587, 607, 619, 643, 647, 659, 683, 787, 823, 827, 839, 907, 911, 947, 983, 1039, 1087, 1091, 1151, 1163, 1187, 1367, 1399
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Programs
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Magma
[p: p in PrimesUpTo(1400) | IsPrime(Floor(p/6))]; // Vincenzo Librandi, Apr 16 2013
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Mathematica
Select[Prime[Range[6! ]],PrimeQ[Floor[ #/6]]&]
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PARI
is(n)=isprime(n) && isprime(n\6) \\ Charles R Greathouse IV, Feb 23 2017
Formula
a(n) >> n log^2 n. - Charles R Greathouse IV, Feb 23 2017
Extensions
Definition corrected by R. J. Mathar, Dec 06 2009