33 lines
673 B
Plaintext
33 lines
673 B
Plaintext
f = DivisorSigma[1, #] - # &;
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limit = 10^5;
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c = Not /@ PrimeQ[Range[limit]];
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slimit = 15 limit;
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s = ConstantArray[False, slimit + 1];
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untouchable = {2, 5};
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Do[
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val = f[i];
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If[val <= slimit,
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s[[val]] = True
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]
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,
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{i, 6, slimit}
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]
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Do[
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If[! s[[n]],
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If[c[[n - 1]],
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If[c[[n - 3]],
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AppendTo[untouchable, n]
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]
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]
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]
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,
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{n, 6, limit, 2}
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]
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Multicolumn[Select[untouchable, LessEqualThan[2000]]]
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Count[untouchable, _?(LessEqualThan[2000])]
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Count[untouchable, _?(LessEqualThan[10])]
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Count[untouchable, _?(LessEqualThan[100])]
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Count[untouchable, _?(LessEqualThan[1000])]
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Count[untouchable, _?(LessEqualThan[10000])]
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Count[untouchable, _?(LessEqualThan[100000])]
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