A306876 Larger of reduced unitary amicable pair.

175742294, 6263852385, 16082297385, 18625120185, 32553626105, 38947446285, 37626449685, 41194817265, 103052922665, 87988279533, 103552755405, 126755126589, 131943742994, 192245655405, 226960409585, 181521732405, 502566224565, 399451768365, 403080683565, 461943100905

Offset: 1

Author

Amiram Eldar, Mar 14 2019

Keywords

• nonn

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).

Examples

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

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

Crossrefs

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

Programs

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