The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A306875 Lesser of reduced unitary amicable pair. 2
 172622505, 6217560734, 16017860054, 18102483014, 20021589510, 31285993970, 32576024810, 39270110990, 68700877014, 80170395410, 81142298930, 99542647490, 125182657005, 144194617490, 153113328654, 181335043274, 318710758730, 374642686418, 378482712530, 455440763414 (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 larger members are in A306876. LINKS Amiram Eldar, Table of n, a(n) for n = 1..28 (terms below 10^12, from David Moews's site). David Moews, Perfect, amicable and sociable numbers J. O. M. Pedersen, Tables of Aliquot Cycles EXAMPLE 172622505 is in the sequence since it is the lesser 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, n]], {n, 1, 10^9}]; s CROSSREFS Cf. A003502, A002952, A126172, A034460, A306876. Sequence in context: A104331 A233598 A187316 * A251999 A003850 A003843 Adjacent sequences: A306872 A306873 A306874 * A306876 A306877 A306878 KEYWORD nonn AUTHOR Amiram Eldar, Mar 14 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 16 11:18 EDT 2024. Contains 375965 sequences. (Running on oeis4.)