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A323252
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Numbers k such that the numerator and denominator of the reduced fraction Sum_{i=1..k} 1/i have no digits in common.
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0
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OFFSET
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1,1
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LINKS
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EXAMPLE
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2 is in the sequence since Sum_{i=1..2} 1/i = 1 + 1/2 = 3/2 and the numerator and denominator have no digits in common.
3 is in the sequence since Sum_{i=1..3} 1/i = 1 + 1/2 + 1/3 = 11/6 and the numerator and denominator have no digits in common.
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MATHEMATICA
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Select[Range@100, Intersection @@ IntegerDigits[ Through[ {Numerator, Denominator}[ HarmonicNumber@ #]]] == {} &] (* Giovanni Resta, Sep 13 2019 *)
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PROG
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(PARI) isok(n) = my(h=sum(k=1, n, 1/k)); #setintersect(Set(digits(numerator(h))), Set(digits(denominator(h)))) == 0; \\ Michel Marcus, Sep 13 2019
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CROSSREFS
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KEYWORD
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nonn,more,base
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AUTHOR
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STATUS
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approved
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