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A242751 Semiprimes having only holey digits (0,4,6,8,9). 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 18 15:25 EDT 2019. Contains 324213 sequences. (Running on oeis4.)