A113623 7-smooth numbers containing only noncomposite digits (1,2,3,5,7).

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

Links

Table of n, a(n) for n=1..47.

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

Adjacent sequences: A113620 A113621 A113622 * A113624 A113625 A113626

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