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A107342
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Semiprimes with semiprime digits (digits 4, 6, 9 only).
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10
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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; internal format)
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OFFSET
| 1,1
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FORMULA
| 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.
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EXAMPLE
| 4 = 2^2
6 = 2 * 3
9 = 3^2
46 = 2 * 23
49 = 7^2
69 = 3 * 23
94 = 2 * 47
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MATHEMATICA
| fQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2 && Union[ Join[{4, 6, 9}, IntegerDigits[n]]] == {4, 6, 9}; Select[ Range[ 47000], fQ[ # ] &] (from Robert G. Wilson v (rgwv(AT)rgwv.com), May 27 2005)
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CROSSREFS
| Cf. A001358, A029581, A107665, A107666, A111494, A111496, A111697.
Sequence in context: A175459 A107665 A085733 * A086698 A115666 A104389
Adjacent sequences: A107339 A107340 A107341 * A107343 A107344 A107345
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KEYWORD
| base,easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), May 22 2005
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), May 27 2005
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