A113623 - OEIS

%I #11 Sep 17 2024 13:57:45

%S 1,2,3,5,7,12,15,21,25,27,32,35,72,75,112,125,135,175,225,252,315,375,

%T 512,525,735,1125,1152,1215,1225,1323,1372,1512,1575,1715,2352,3125,

%U 3375,13122,13125,15552,25515,25725,31752,35721,55125,77175,111132

%N 7-smooth numbers containing only noncomposite digits (1,2,3,5,7).

%e 175 is a term since 175 = 5^2*7 and contains digits 1,5,7 none of which is composite. 175 is a member of A002473.

%p isA002473 := proc(n) local ifs ; if n <= 10 then true ; else ifs := ifactors(n)[2] ; if max( seq(op(1,i),i=ifs) ) <= 7 then true; else false ; fi ; fi ; end: isA113623 := proc(n) local digs ; if isA002473(n) then if convert(convert(n,base,10),set) minus {1,2,3,5,7} <> {} then false ; else true ; fi ; else false ; fi ; end: for n from 1 to 150000 do if isA113623(n) then printf("%d, ",n) ; fi ; od; # _R. J. Mathar_, Aug 28 2007

%Y Intersection of A001742 and A002473.

%Y Cf. A113624.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Nov 10 2005

%E More terms from _R. J. Mathar_, Aug 28 2007

%E Name corrected by _Andrew Howroyd_, Sep 17 2024