A107665 Numbers with semiprime digits (digits 4, 6, 9 only).

4, 6, 9, 44, 46, 49, 64, 66, 69, 94, 96, 99, 444, 446, 449, 464, 466, 469, 494, 496, 499, 644, 646, 649, 664, 666, 669, 694, 696, 699, 944, 946, 949, 964, 966, 969, 994, 996, 999, 4444, 4446, 4449, 4464, 4466, 4469, 4494, 4496, 4499, 4644, 4646, 4649, 4664

Offset: 1

Author

Rick L. Shepherd, May 19 2005

Keywords

• base
• nonn

Crossrefs

Cf. A107666 (primes in this sequence), A001358 (semiprimes), A029581 (all digits are composite).

Cf. A107342, A111494, A111496, A111697.

Programs

Mathematica

Select[Range[5000],Union[Pick[DigitCount[#],{1,1,1,0,1,0,1,1,0,1},1]] == {0}&] (* Harvey P. Dale, Oct 21 2011 *)
Flatten[Table[FromDigits/@Tuples[{4,6,9},n],{n,4}]] (* Harvey P. Dale, Oct 21 2014 *)