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A293187
Bi-unitary 3-abundant numbers: numbers k such that bsigma(k) > 3*k, where bsigma is the sum of the bi-unitary divisors function (A188999).
3
480, 840, 1080, 1320, 1512, 1560, 1680, 1848, 1890, 1920, 2040, 2184, 2280, 2376, 2688, 2760, 2856, 3000, 3192, 3240, 3360, 3480, 3720, 3840, 4320, 4440, 4920, 5160, 5280, 5640, 5880, 6048, 6240, 6360, 6720, 7080, 7320, 7392, 7560, 7680, 8040, 8160, 8520
OFFSET
1,1
COMMENTS
Analogous to 3-abundant numbers (A023197) with bi-unitary sigma (A188999) instead of sigma (A000203).
LINKS
EXAMPLE
480 is in the sequence since bi-unitary sigma(480) = 1512 > 3 * 480.
MATHEMATICA
f[n_] := Select[Divisors[n], Function[d, CoprimeQ[d, n/d]]]; bsigma[m_] := DivisorSum[m, # &, Last@Intersection[f@#, f[m/#]] == 1 &]; bAbundantQ[n_] := bsigma[n] > 3 n; Select[Range[1000], bAbundantQ] (* after Michael De Vlieger at A188999 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 01 2017
STATUS
approved