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A306876 Larger of reduced unitary amicable pair. 2
175742294, 6263852385, 16082297385, 18625120185, 32553626105, 38947446285, 37626449685, 41194817265, 103052922665, 87988279533, 103552755405, 126755126589, 131943742994, 192245655405, 226960409585, 181521732405, 502566224565, 399451768365, 403080683565, 461943100905 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A pair m < n is a reduced unitary amicable pair if usigma(m) = usigma(n) = m + n + 1, where usigma(n) is the sum of unitary divisors of n (A034460). The terms are ordered according to their lesser counterparts (A306875).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..28 (terms with lesser member below 10^12, from David Moews's site).

David Moews, Perfect, amicable and sociable numbers

J. O. M. Pedersen, Tables of Aliquot Cycles

EXAMPLE

175742294 is in the sequence since it is the larger of the amicable pair (172622505, 175742294): usigma(172622505) = usigma(175742294) = 348364800 = 172622505 + 175742294 + 1.

MATHEMATICA

us[n_] := Times @@ (1 + Power @@@ FactorInteger[n]) - n;  s={}; Do[m = us[n] - 1; If[m > n && us[m] == n + 1, AppendTo[s, m]], {n, 1, 10^9}]; s

CROSSREFS

Cf. A003503, A002953, A126173, A034460, A306875.

Sequence in context: A093046 A323056 A300555 * A213966 A206520 A127955

Adjacent sequences:  A306873 A306874 A306875 * A306877 A306878 A306879

KEYWORD

nonn

AUTHOR

Amiram Eldar, Mar 14 2019

STATUS

approved

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Last modified February 21 02:02 EST 2020. Contains 332086 sequences. (Running on oeis4.)