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

Author

Amiram Eldar, Oct 01 2017

Keywords

• nonn

Comments

Analogous to 3-abundant numbers (A023197) with bi-unitary sigma (A188999) instead of sigma (A000203).

Examples

			480 is in the sequence since bi-unitary sigma(480) = 1512 > 3 * 480.
		

Links

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

Crossrefs

Cf. A023197, A285615, A188999, A292982.

Programs

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 *)