The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 (list; graph; refs; listen; history; text; internal format)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 16 10:30 EDT 2021. Contains 343941 sequences. (Running on oeis4.)