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A036315
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Composite numbers whose prime factors contain no digits other than 3 and 5.
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2
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9, 15, 25, 27, 45, 75, 81, 125, 135, 159, 225, 243, 265, 375, 405, 477, 625, 675, 729, 795, 1059, 1125, 1215, 1325, 1431, 1765, 1875, 2025, 2187, 2385, 2809, 3125, 3177, 3375, 3645, 3975, 4293, 5295, 5625, 6075, 6561, 6625, 7155, 8427, 8825, 9375, 9531
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n) = Product_{p in A020462} (p/(p - 1)) - Sum_{p in A020462} 1/p - 1 = 0.3620363317... . - Amiram Eldar, May 22 2022
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MATHEMATICA
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Select[Range[10000], SubsetQ[{3, 5}, Union[Flatten[IntegerDigits/@ FactorInteger[ #][[All, 1]]]]]&&CompositeQ[#]&] (* Harvey P. Dale, May 30 2021 *)
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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