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

1,1

Links

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A001097, A001359, A006512.

Sequence in context: A304275 A031072 A193880 * A361484 A054692 A056256

Adjacent sequences: A138245 A138246 A138247 * A138249 A138250 A138251

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, May 05 2008

Status

approved