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A329461
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Poulet numbers (Fermat pseudoprimes to base 2) k, whose sum of proper divisors sigma(k)-k is also a Poulet number.
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1
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513629, 3898129, 42656440661, 44368051087, 281257598737, 1746990146513, 5179966705541, 6275022424667, 9980519428181, 28343625432959, 37300616980817, 38107619098709, 55964206116901, 73114593538031, 123729699419917, 161656112395553, 297792380089151, 404770747208591
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OFFSET
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1,1
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COMMENTS
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The corresponding sums of proper divisors are 2047, 4371, 476971, 526593, 1325843, 5919187, 5256091, 6631549, 7295851, 18007345, 31166803, 17641207, 10274913907, 73562833, 27808463, 68512867, 48269761, 75501793, ...
There are 72 terms below 2^64, 71 of them have 2 prime factors, and only one has 3 prime factors: 55964206116901 = 6361 * 47701 * 184441.
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LINKS
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EXAMPLE
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513629 is a Poulet number, and sigma(513629)-513629 = 2047 is also a Poulet number.
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MATHEMATICA
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pouletQ[n_] := CompositeQ[n ]&& PowerMod[2, n - 1, n] == 1; s[n_] := DivisorSigma[ 1, n] - n; seq={}; Do[If[pouletQ[n] && pouletQ[s[n]], AppendTo[seq, n]], {n, 1, 10^7}]; seq
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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