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A113623
7-smooth numbers containing only noncomposite digits (1,2,3,5,7).
1
1, 2, 3, 5, 7, 12, 15, 21, 25, 27, 32, 35, 72, 75, 112, 125, 135, 175, 225, 252, 315, 375, 512, 525, 735, 1125, 1152, 1215, 1225, 1323, 1372, 1512, 1575, 1715, 2352, 3125, 3375, 13122, 13125, 15552, 25515, 25725, 31752, 35721, 55125, 77175, 111132
OFFSET
1,2
EXAMPLE
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.
MAPLE
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
CROSSREFS
Intersection of A001742 and A002473.
Cf. A113624.
Sequence in context: A309370 A022438 A193760 * A308868 A361459 A078912
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 10 2005
EXTENSIONS
More terms from R. J. Mathar, Aug 28 2007
Name corrected by Andrew Howroyd, Sep 17 2024
STATUS
approved