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).

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

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

Cf. A023197, A285615, A188999, A292982.

Sequence in context: A257415 A179667 A108876 * A206200 A258558 A083728

Adjacent sequences: A293184 A293185 A293186 * A293188 A293189 A293190

Keyword

nonn

Author

Amiram Eldar, Oct 01 2017

Status

approved