A138248 Prime numbers k such that 18*k - 1 and 18*k + 1 are twin primes.

11, 29, 59, 71, 181, 199, 241, 251, 431, 491, 809, 991, 1051, 1109, 1151, 1231, 1249, 1289, 1319, 1459, 1571, 1931, 1949, 2099, 2411, 2729, 2909, 2939, 3301, 3461, 3499, 3511, 3881, 3889, 4201, 4231, 4651, 4679, 4721, 4889, 5011, 5081, 5209, 5639, 6299

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 05 2008

Keywords

• nonn

Examples

			11*18 - 1 = 197 (prime), 11*18 + 1 = 199 (prime).
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001097, A001359, A006512.

Programs

Magma

[n: n in [0..10000] |IsPrime(n) and IsPrime(18*n-1)and IsPrime(18*n+1)] // Vincenzo Librandi, Aug 03 2010

Mathematica

a=18;Select[Prime[Range[250]],PrimeQ[a*#-1]&&PrimeQ[a*#+1] &]

Python

from sympy import isprime, primerange
def ok(p): return isprime(18*p-1) and isprime(18*p+1)
def aupto(limit): return [p for p in primerange(1, limit+1) if ok(p)]
print(aupto(6299)) # Michael S. Branicky, Nov 29 2021