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 A306871 Larger of reduced bi-unitary amicable pair. 2
 2295, 20735, 75495, 1148735, 817479, 774375, 1902215, 1341495, 1348935, 2226014, 2421704, 3123735, 3010215, 5644415, 3894344, 4282215, 4994055, 7509159, 12251679, 10106504, 12900734, 20444319, 24519159, 28206815, 31356314, 33362175, 41950359, 36129375, 43321095 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A pair m < n are 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 terms are ordered according to their lesser counterparts (A306870). LINKS Amiram Eldar, Table of n, a(n) for n = 1..528 (terms with lesser member below 2*10^11, from David Moews's site). David Moews, Perfect, amicable and sociable numbers. EXAMPLE 2295 is in the sequence since it is the larger 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, m]], {n, 1, 10^7}]; s CROSSREFS Cf. A003503, A126173, A188999, A292981, A306870. Sequence in context: A163513 A349085 A274359 * A123911 A126173 A083572 Adjacent sequences: A306868 A306869 A306870 * A306872 A306873 A306874 KEYWORD nonn AUTHOR Amiram Eldar, Mar 14 2019 STATUS approved

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Last modified May 19 13:25 EDT 2024. Contains 372694 sequences. (Running on oeis4.)