A165810 Primes p such that 18*p+1 is also a prime.
2, 7, 11, 17, 29, 41, 59, 71, 79, 97, 127, 137, 139, 149, 151, 181, 197, 199, 241, 251, 277, 281, 307, 337, 347, 367, 379, 401, 431, 479, 491, 541, 569, 587, 659, 701, 709, 757, 797, 809, 821, 827, 829, 857, 877, 881, 947, 991, 1021, 1051, 1109, 1117, 1129, 1151, 1229
Offset: 1
Examples
For p=2, 18*p+1=37. For p=7, 18*p+1=127. For p=11, 18*p+1=199.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
Select[Prime[Range[1000]],PrimeQ[18#+1]&] (* Harvey P. Dale, Mar 06 2011 *)
Formula
a(n) = (A165811(n)-1)/18.
Extensions
Extended by R. J. Mathar, Oct 16 2009