A242751 Semiprimes having only holey digits (0,4,6,8,9).

4, 6, 9, 46, 49, 69, 86, 94, 446, 466, 469, 489, 649, 669, 689, 694, 698, 699, 849, 866, 869, 886, 889, 898, 899, 949, 989, 998, 4006, 4009, 4069, 4406, 4449, 4469, 4486, 4489, 4499, 4609, 4666, 4694, 4699, 4846, 4849, 4894, 4946, 4989, 6009, 6046, 6049, 6098

Offset

1,1

Links

K. D. Bajpai, Table of n, a(n) for n = 1..8612

Example

4609 = 11 * 419 is semiprime and has only holey digits 4, 6, 0 and 9. Hence it is in the sequence.
4849 = 13 * 373 is semiprime and has only holey digits 4, 8, 4 and 9. Hence it is in the sequence.

Mathematica

c = 0; Do[a = PrimeOmega[n]; If[a==2&& Intersection[IntegerDigits[n], {1, 2, 3, 5, 7}]=={}, c++; Print[c, "  ", n]], {n, 2*10^7}]
Select[FromDigits/@Tuples[{0, 4, 6, 8, 9}, 4], PrimeOmega[#]==2&] (* Harvey P. Dale, Sep 08 2017 *)

Crossrefs

Cf. A001358, A061372.

Sequence in context: A257652 A107665 A085733 * A107342 A086698 A317248

Adjacent sequences: A242748 A242749 A242750 * A242752 A242753 A242754

Keyword

nonn,base

Author

K. D. Bajpai, May 21 2014

Status

approved