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Amiram Eldar, <a href="/A057710/b057710_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
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Amiram Eldar, <a href="/A057710/b057710_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
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Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RestrictedDivisorFunction.html">Restricted Divisor Function</a>.
Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AliquotSequence.html">Aliquot sequence.</a>.
14 is a member of the sequence because s(22) = 14 and s(169) = 14 (and because no other integer x satisfies s(x) = 14).
Positive integers n k with exactly 2 aliquot sequence predecessors. In other words, there are exactly two solutions x for which s(x) = n. The function s(x) here refers to the Restricted Divisor Function, is the sum of all proper divisors of x (A001065).
Amiram Eldar, <a href="/A057710/b057710_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
T. D. Noe, Amiram Eldar, <a href="/A057710/b057710_1.txt">Table of n, a(n) for n = 1..100010000</a>
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len = max = 57; f[_List] := (s = Select[ Split[ Sort[ Table[ DivisorSigma[1, n] - n, {n, 1, max *= 2}]]], Length[#] == 2 & ][[All, 1]]; s [[1 ;; Min[len, Length[s]]]]); FixedPoint[f, {}] (* From _Jean-François Alcover, _, Oct 07 2011 *)
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