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A306870 Lesser of reduced bi-unitary amicable pair. 2
2024, 9504, 62744, 496320, 573560, 677144, 1000824, 1173704, 1208504, 1921185, 2140215, 2198504, 2312024, 2580864, 3847095, 4012184, 4682744, 5416280, 6618080, 9247095, 12500865, 12970880, 13496840, 14371104, 23939685, 25942784, 26409320, 28644704, 34093304 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A pair m < n is a reduced bi-unitary amicable pair if bsigma(m) = bsigma(n) = m + n + 1, where bsigma(n) is the sum of bi-unitary divisors of n (A188999).

The larger members are in A306871.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..528 (terms below 2*10^11, from David Moews's site).

David Moews, Perfect, amicable and sociable numbers.

EXAMPLE

2024 is in the sequence since it is the lesser of the amicable pair (2024, 2295): bsigma(2024) = bsigma(2295) = 4320 = 2024 + 2295 + 1.

MATHEMATICA

fun[p_, e_]:=If[OddQ[e], (p^(e+1)-1)/(p-1), (p^(e+1)-1)/(p-1)-p^(e/2)]; bsigma[1] = 1; bsigma[n_] := Times @@ (fun @@@ FactorInteger[n]); f[n_] := bsigma[n] - n - 1; s={}; Do[m = f[n]; If[m > n && f[m] == n, AppendTo[s, n]], {n, 1, 10^7}]; s

CROSSREFS

Cf. A003502, A126172, A188999, A292980, A306871.

Sequence in context: A126821 A333057 A156855 * A126172 A183999 A250811

Adjacent sequences:  A306867 A306868 A306869 * A306871 A306872 A306873

KEYWORD

nonn

AUTHOR

Amiram Eldar, Mar 14 2019

STATUS

approved

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Last modified August 8 12:21 EDT 2022. Contains 356009 sequences. (Running on oeis4.)