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A107342 Semiprimes with semiprime digits (digits 4, 6, 9 only). 12
4, 6, 9, 46, 49, 69, 94, 446, 466, 469, 649, 669, 694, 699, 949, 4449, 4469, 4499, 4666, 4694, 4699, 4946, 6499, 6646, 6649, 6694, 6999, 9446, 9449, 9466, 9469, 9946, 9969, 44494, 44669, 44949, 44966, 44969, 44999, 46469, 46666, 46946, 46969, 46994 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that all digits of n are elements of A001358 and n is an element of A001358.

Numbers n such that n is an element of A107665 and n is an element of A001358.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..600

EXAMPLE

4 = 2^2

6 = 2 * 3

9 = 3^2

46 = 2 * 23

49 = 7^2

69 = 3 * 23

94 = 2 * 47

MATHEMATICA

fQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2 && Union[ Join[{4, 6, 9}, IntegerDigits[n]]] == {4, 6, 9}; Select[ Range[ 47000], fQ[ # ] &] (* Robert G. Wilson v, May 27 2005 *)

Flatten[Table[Select[FromDigits/@Tuples[{4, 6, 9}, n], PrimeOmega[#]==2&], {n, 5}]] (* Harvey P. Dale, Jun 14 2015 *)

CROSSREFS

Cf. A001358, A029581, A107665, A107666, A111494, A111496, A111697.

Cf. A254715. - Zak Seidov, Feb 06 2015

Sequence in context: A107665 A085733 A242751 * A086698 A115666 A245044

Adjacent sequences:  A107339 A107340 A107341 * A107343 A107344 A107345

KEYWORD

base,easy,nonn

AUTHOR

Jonathan Vos Post, May 22 2005

EXTENSIONS

More terms from Robert G. Wilson v, May 27 2005

STATUS

approved

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Last modified March 28 05:07 EDT 2017. Contains 284182 sequences.