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

1,2

Links

Table of n, a(n) for n=1..58.

Example

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

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 *)

Crossrefs

Subsequence of A014076.

Sequence in context: A067800 A155474 A100819 * A046350 A225438 A175076

Adjacent sequences: A046443 A046444 A046445 * A046447 A046448 A046449

Keyword

nonn,easy,base

Author

Patrick De Geest, Jul 15 1998

Extensions

Definition clarified by Harvey P. Dale, Jul 07 2018

Status

approved