A245590 - OEIS

%I #10 Aug 09 2014 23:08:41

%S 2,3,7,17,23,41,47,53,59,101,149,157,173,179,193,211,229,233,239,241,

%T 251,311,347,349,353,359,373,379,383,389,409,421,439,443,457,479,499,

%U 509,521,541,571,577,599,619,641,661,691,701,719,751,761,769,809,823,829

%N Primes p such that p^2 + 6 is a semiprime.

%H K. D. Bajpai, <a href="/A245590/b245590.txt">Table of n, a(n) for n = 1..11200</a>

%e 7 is in the sequence because it is prime and 7^2 + 6 = 55 = 5 * 11, which is semiprime.

%e 23 is in the sequence because it is prime and 23^2 + 6 = 535 = 5 * 107, which is semiprime.

%p with(numtheory):A245590:=n->`if`(isprime(n) and bigomega(n^2+6)=2, n, NULL): seq(A245590 (n), n=1..1500);

%t Select[Prime[Range[200]], PrimeOmega[#^2 + 6] == 2 &]

%o (PARI)

%o forprime(p=1,10^4,if(bigomega(p^2+6)==2,print1(p,", "))) \\ _Derek Orr_, Aug 03 2014

%Y Cf. A000040, A001358.

%Y Cf. A109953 (primes p: p^2 + 2 is semiprime).

%Y Cf. A243365 (primes p: p^2 + 6 and p^2 - 6  are semiprimes).

%K nonn,easy

%O 1,1

%A _K. D. Bajpai_, Jul 26 2014