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%I #7 Jul 02 2017 02:33:47
%S 2,5,11,17,29,31,47,53,61,73,83,89,107,137,139,151,157,173,179,181,
%T 197,199,211,233,263,283,317,331,337,367,373,389,409,433,443,449,467,
%U 523,541,547,569,577,587,593,607,619,631,677,683,691,709,719,727,733,751,787,809,811,827
%N Primes p such that p + 4 is a semiprime.
%C Except for case p=5, p+4 is never a perfect square.
%C For p = {2, 11, 31, 73, 139, 433, 1759, 2017} p+4 is a product of two consecutive primes.
%H Charles R Greathouse IV, <a href="/A289250/b289250.txt">Table of n, a(n) for n = 1..10000</a>
%e 2+4=6=2*3, 5+4=9=3*3, 11+4=15=3*5 (all semiprimes).
%t Select[Prime@ Range@ 150, PrimeOmega[# + 4] == 2 &] (* _Michael De Vlieger_, Jun 29 2017 *)
%o (PARI) issemi(n)=bigomega(n)==2
%o is(n)=isprime(n) && issemi(n+4) \\ _Charles R Greathouse IV_, Jul 02 2017
%Y Cf. A001358, A063637, A082919, A241484,
%K nonn
%O 1,1
%A _Zak Seidov_, Jun 29 2017
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