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A046446 Nonprimes whose prime factors contain only odd digits.

%I A046446 #17 Oct 13 2019 02:32:45
%S A046446 1,9,15,21,25,27,33,35,39,45,49,51,55,57,63,65,75,77,81,85,91,93,95,
%T A046446 99,105,111,117,119,121,125,133,135,143,147,153,155,159,165,169,171,
%U A046446 175,177,185,187,189,195,209,213,217,219,221,225,231,237,243,245,247,255
%N A046446 Nonprimes whose prime factors contain only odd digits.
%e A046446 247 = 13 * 19; 1, 3 and 9 are odd digits.
%p A046446 isA046446 := proc(n)
%p A046446     if not isprime(n) then
%p A046446         fset := numtheory[factorset](n) ;
%p A046446         for f in fset do
%p A046446             convert(convert(f,base,10),set) ;
%p A046446             if % intersect {0,2,4,6,8} <> {} then
%p A046446                 return false;
%p A046446             end if;
%p A046446         end do:
%p A046446         true ;
%p A046446     else
%p A046446         false;
%p A046446     end if;
%p A046446 end proc:
%p A046446 for n from 1 to 260 do
%p A046446     if isA046446(n) then
%p A046446         printf("%d,",n) ;
%p A046446     end if;
%p A046446 end do: # _R. J. Mathar_, Oct 02 2018
%t A046446 Select[Range[255], ! PrimeQ[#] && And @@ OddQ[Union[Flatten[IntegerDigits[First /@ FactorInteger[#]]]]] &] (* _Jayanta Basu_, Jun 24 2013 *)
%Y A046446 Subsequence of A014076.
%K A046446 nonn,easy,base
%O A046446 1,2
%A A046446 _Patrick De Geest_, Jul 15 1998
%E A046446 Definition clarified by _Harvey P. Dale_, Jul 07 2018