login
Numbers of the form 2p or 3p where p is a prime greater than 3.
2

%I #9 Dec 26 2014 17:35:41

%S 10,14,15,21,22,26,33,34,38,39,46,51,57,58,62,69,74,82,86,87,93,94,

%T 106,111,118,122,123,129,134,141,142,146,158,159,166,177,178,183,194,

%U 201,202,206,213,214,218,219,226,237,249,254,262,267,274,278,291,298,302

%N Numbers of the form 2p or 3p where p is a prime greater than 3.

%C Squarefree semiprimes (A006881) which have exactly one prime factor <=3 [_R. J. Mathar_, Dec 09 2009]

%p isA171156 := proc(n) local f; f := numtheory[factorset](n) ; if numtheory[bigomega](n) = 2 and nops(f) = 2 then if f = {2,3} then false; else (n mod 2) = 0 or (n mod 3) = 0 ; fi; else false; fi; end:

%p for n from 10 to 500 do if isA171156(n) then printf("%d,",n) ; fi; od: # _R. J. Mathar_, Dec 09 2009

%Y Cf. A253106, A001748, A100484.

%K nonn,easy,less

%O 1,1

%A _Juri-Stepan Gerasimov_, Dec 04 2009

%E Edited by _Charles R Greathouse IV_, Mar 25 2010