A226754 - OEIS

%I #19 Jul 03 2021 14:10:57

%S 14,65,119,377,629,779,1769,3827,4559,5777,9179,10877,16109,19109,

%T 25877,32639,37949,39059,49769,56279,60377,75077,78209,79799,100127,

%U 103739,105569,145529,154289,161027,189419,228149,244649,250277,288419,294527,316409,335789

%N Numbers of the form p*q, p and q prime with q=2*p+3.

%H Charles R Greathouse IV, <a href="/A226754/b226754.txt">Table of n, a(n) for n = 1..10000</a>

%t fa = FactorInteger; t[n_]:=Length[fa[n]] == 2 && fa[n][[1,2]]== fa[n][[2, 2]] == 1 && 2 fa[n][[1, 1]]+3 == fa[n][[2, 1]];Select[1+Range[200000], t]

%t Times@@#&/@Select[Table[{p,2p+3},{p,Prime[Range[200]]}],PrimeQ[#[[2]]]&] (* _Harvey P. Dale_, Jul 03 2021 *)

%o (PARI) list(lim)=my(v=List(),q); forprime(p=2,(sqrt(8*lim+9)-3)\4, if(isprime(q=2*p+3),listput(v,p*q))); Vec(v) \\ _Charles R Greathouse IV_, Nov 19 2013

%Y Cf. A129521, A156592, A226755.

%K nonn

%O 1,1

%A _José María Grau Ribas_, Jun 16 2013