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A292984
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Bi-unitary superabundant numbers: numbers n such that bsigma(n)/n > bsigma(m)/m for all m < n, where bsigma is the sum of the bi-unitary divisors function (A188999).
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5
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1, 2, 6, 24, 96, 120, 480, 840, 3360, 7560, 30240, 83160, 332640, 1081080, 4324320, 17297280, 69189120, 73513440, 294053760, 1176215040, 1396755360, 5587021440
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OFFSET
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1,2
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COMMENTS
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Analogous to superabundant numbers (A004394) with bi-unitary sigma (A188999) instead of sigma (A000203).
The least bi-unitary k-abundant number (bsigma(m)/m > k*m) for k = 1, 2, ... is 1, 24, 480, 83160, 294053760. - Amiram Eldar, Dec 05 2018
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LINKS
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Table of n, a(n) for n=1..22.
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MATHEMATICA
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fun[p_, e_]:=If[OddQ[e], (p^(e+1)-1)/(p-1), (p^(e+1)-1)/(p-1)-p^(e/2)]; bsigma[n_] := If[n==1, 1, Times @@ (fun @@@ FactorInteger[n])]; a = {}; rmax = 0; Do[r = bsigma[n]/n; If[r > rmax, AppendTo[a, n]; rmax = r], {n, 1000}]; a
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CROSSREFS
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Cf. A004394, A188999.
Sequence in context: A192466 A115220 A293185 * A072854 A147944 A147935
Adjacent sequences: A292981 A292982 A292983 * A292985 A292986 A292987
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KEYWORD
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nonn,more
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AUTHOR
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Amiram Eldar, Sep 27 2017
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EXTENSIONS
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a(14)-a(22) from Amiram Eldar, Dec 06 2018
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STATUS
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approved
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