22 lines
787 B
Raku
22 lines
787 B
Raku
use Prime::Factor;
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sub μ (Int \n) {
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return 0 if n %% 4 or n %% 9 or n %% 25 or n %% 49 or n %% 121;
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my @p = prime-factors(n);
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+@p == +@p.unique ?? +@p %% 2 ?? 1 !! -1 !! 0
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}
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my @mertens = lazy [\+] flat '', 1, (2..*).hyper.map: -> \n { μ(n) };
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put "Mertens sequence - First 199 terms:\n",
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@mertens[^200]».fmt('%3s').batch(20).join("\n"),
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"\n\nEquals zero ", +@mertens[1..1000].grep( !* ),
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' times between 1 and 1000', "\n\nCrosses zero ",
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+@mertens[1..1000].kv.grep( {!$^v and @mertens[$^k]} ),
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" times between 1 and 1000\n\nFirst Mertens equal to:";
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for 10, 20, 30 … 100 -> $threshold {
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printf "%4d: M(%d)\n", -$threshold, @mertens.first: * == -$threshold, :k;
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printf "%4d: M(%d)\n", $threshold, @mertens.first: * == $threshold, :k;
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}
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