A293183 Numbers k such that bsigma(k) = bsigma(k+1), where bsigma(k) is the sum of the bi-unitary divisors of k (A188999).

14, 27, 44, 459, 620, 957, 1334, 1634, 1652, 2204, 2685, 3195, 3451, 3956, 5547, 8636, 8907, 9844, 11515, 11745, 16874, 19491, 20145, 20155, 27643, 31724, 33998, 38180, 41265, 41547, 42818, 45716, 48364, 64665, 74875, 74918, 79316, 79826, 79833, 83780, 84134

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..2148 (terms below 2*10^10)

Example

14 is in the sequence since bsigma(14) = bsigma(15) = 24.

Mathematica

f[n_] := Select[Divisors[n], Function[d, CoprimeQ[d, n/d]]]; bsigma[m_] :=
DivisorSum[m, # &, Last@Intersection[f@#, f[m/#]] == 1 &]; a = {}; b1 = 0; Do[b2 = bsigma[k]; If[b1 == b2, a = AppendTo[a, k - 1]]; b1 = b2, {k, 1, 10^6}]; a (* after Michael De Vlieger at A188999 *)

Crossrefs

Cf. A002961, A064125, A188999.

Sequence in context: A086451 A190991 A306985 * A370119 A168596 A275251

Adjacent sequences: A293180 A293181 A293182 * A293184 A293185 A293186

Keyword

nonn

Author

Amiram Eldar, Oct 01 2017

Status

approved