A363374 - OEIS

%I #11 Dec 14 2024 15:54:52

%S 8,11,13,15,17,18,21,23,25,30,32,33,34,35,36,37,40,44,54,58,60,61,71,

%T 73,92,95,101,102,106,144,160,164,183,200,209,210,216,241,244,270,273,

%U 274,281,293,309,313,344,365,422,430,461,475,477,480,504,509,556,579,597,609,612,631,650

%N Numbers k such that 2^k - 3 is a semiprime.

%C The numbers 717, 720, 759 are also terms with 713 being the only remaining unknown below them.

%e 11 is a member because 2^11 - 3 = 2045 = 5 * 409 is a semiprime.

%t Select[Range[700],PrimeOmega[2^#-3]==2&] (* _Harvey P. Dale_, Dec 14 2024 *)

%Y Cf. A085724.

%K nonn

%O 1,1

%A _Kevin P. Thompson_, May 29 2023