|
|
A194593
|
|
Semiprimes s such that phi(s)/2 is prime.
|
|
4
|
|
|
9, 10, 14, 22, 46, 94, 118, 166, 214, 334, 358, 454, 526, 694, 718, 766, 934, 958, 1006, 1126, 1174, 1438, 1678, 1726, 1774, 1966, 2038, 2374, 2566, 2614, 2638, 2734, 2878, 2974, 3046, 3238, 3646, 3814, 4054, 4078, 4126, 4198, 4414, 4894, 4918, 5158, 5638, 5758, 5806, 5926, 5998
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
|
|
MAPLE
|
9, 10, op(select(s -> isprime(s/2) and isprime((s-2)/4), [seq(s, s=6..10000, 8)])); # Robert Israel, Apr 06 2016
|
|
MATHEMATICA
|
Select[Range@ 6000, PrimeOmega@ # == 2 && PrimeQ[EulerPhi[#]/2] &] (* Michael De Vlieger, Apr 06 2016 *)
|
|
PROG
|
(PARI) isok(n) = (bigomega(n)== 2) && isprime(eulerphi(n)/2); \\ Michel Marcus, Apr 06 2016
(Magma) [9] cat [2*p: p in PrimesUpTo(3000) | IsPrime((p - 1) div 2)]; // Vincenzo Librandi, Aug 25 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|