login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A247590 Primes p such that p + 6^k is also prime at least for k = 1, 2, 3 and 4. 1
7, 11, 23, 131, 157, 193, 227, 271, 331, 571, 947, 977, 1013, 1087, 1283, 1453, 1657, 1871, 2341, 2671, 2693, 3607, 3637, 3691, 4013, 4951, 5407, 5653, 6211, 6353, 6653, 6827, 6977, 6991, 7541, 7717, 8053, 8081, 8537, 9203, 9613, 9643, 10853, 11113, 11251, 11933 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
a(1) = 7 is prime. 7 + 6^1 = 13, 7 + 6^2 = 43, 7 + 6^3 = 223 and 7 + 6^4 = 1303 are also prime. It is the smallest such set of 5 primes; (Quintet).
MATHEMATICA
Select[k = {1, 2, 3, 4}; Prime[Range[500]], And @@ PrimeQ[# + 6^k] &]
PROG
(PARI)
forprime(p=1, 10^4, c=1; for(k=1, 4, if(!isprime(p+6^k), c--; break)); if(c, print1(p, ", "))) \\ Derek Orr, Sep 20 2014
CROSSREFS
Sequence in context: A076855 A160054 A359414 * A027830 A134043 A102373
KEYWORD
nonn,easy
AUTHOR
K. D. Bajpai, Sep 20 2014
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 26 02:01 EST 2024. Contains 370335 sequences. (Running on oeis4.)