A046446 Nonprimes whose prime factors contain only odd digits.

1, 9, 15, 21, 25, 27, 33, 35, 39, 45, 49, 51, 55, 57, 63, 65, 75, 77, 81, 85, 91, 93, 95, 99, 105, 111, 117, 119, 121, 125, 133, 135, 143, 147, 153, 155, 159, 165, 169, 171, 175, 177, 185, 187, 189, 195, 209, 213, 217, 219, 221, 225, 231, 237, 243, 245, 247, 255

Offset: 1

Author

Patrick De Geest, Jul 15 1998

Keywords

• nonn
• easy
• base

Examples

			247 = 13 * 19; 1, 3 and 9 are odd digits.
		

Crossrefs

Subsequence of A014076.

Programs

Maple

isA046446 := proc(n)
    if not isprime(n) then
        fset := numtheory[factorset](n) ;
        for f in fset do
            convert(convert(f,base,10),set) ;
            if % intersect {0,2,4,6,8} <> {} then
                return false;
            end if;
        end do:
        true ;
    else
        false;
    end if;
end proc:
for n from 1 to 260 do
    if isA046446(n) then
        printf("%d,",n) ;
    end if;
end do: # R. J. Mathar, Oct 02 2018

Mathematica

Select[Range[255], ! PrimeQ[#] && And @@ OddQ[Union[Flatten[IntegerDigits[First /@ FactorInteger[#]]]]] &] (* Jayanta Basu, Jun 24 2013 *)

Extensions

Definition clarified by Harvey P. Dale, Jul 07 2018