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!)
A165986 Even semiprimes n such that (the largest prime factor of n) + 4 is prime. 2
6, 14, 26, 38, 74, 86, 134, 158, 194, 206, 218, 254, 326, 386, 446, 458, 554, 614, 626, 698, 758, 794, 878, 914, 926, 974, 998, 1226, 1286, 1346, 1478, 1514, 1538, 1646, 1706, 1718, 1754, 1766, 1814, 1874, 1934, 2018, 2174, 2186, 2426, 2558, 2594, 2606 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Also numbers n of the form 2p such that p and p+4 are prime.
n is congruent to 2 modulo 3 for n > 6.
LINKS
FORMULA
a(n) = 2*A023200(n). - R. J. Mathar, Jun 23 2011
MATHEMATICA
Select[Range[2, 3000, 2], PrimeOmega[#]==2&&PrimeQ[FactorInteger[#][[-1, 1]]+4]&] (* Harvey P. Dale, Mar 09 2021 *)
PROG
(Magma) [ 2*p: p in PrimesUpTo(1500) | IsPrime(p+4) ]; // Klaus Brockhaus, Jun 26 2011
(PARI) forprime(p=2, 1e3, if(isprime(p+4), print1(p+p", "))) \\ Charles R Greathouse IV, Jun 26 2011
CROSSREFS
Sequence in context: A293400 A026055 A288939 * A292670 A131951 A168648
KEYWORD
nonn,easy
AUTHOR
Giovanni Teofilatto, Oct 03 2009, Jun 26 2011
EXTENSIONS
Definition clarified by Harvey P. Dale, Jul 14 2021
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 April 24 06:07 EDT 2024. Contains 371918 sequences. (Running on oeis4.)