A new method for finding amicable pairs:

Abstract: "Let [sigma](x) denote the sum of all divisors of the (positive) integer x. An amicable pair is a pair of integers (m,n) with m < n such that [sigma](m) = [sigma](n) = m + n. The smallest amicable pair is (220,284). A new method for finding amicable pairs is presented, based on the...

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Bibliographische Detailangaben
1. Verfasser: Riele, Herman J. te (VerfasserIn)
Format: Buch
Sprache:English
Veröffentlicht: Amsterdam 1995
Schriftenreihe:Centrum voor Wiskunde en Informatica <Amsterdam> / Afdeling Numerieke Wiskunde: Report NM 1995,12
Schlagworte:
Zusammenfassung:Abstract: "Let [sigma](x) denote the sum of all divisors of the (positive) integer x. An amicable pair is a pair of integers (m,n) with m < n such that [sigma](m) = [sigma](n) = m + n. The smallest amicable pair is (220,284). A new method for finding amicable pairs is presented, based on the following observation of Erdős: For given s, let x₁, x₂,... be solutions of the equation [sigma](x) = s, then any pair (x[subscript i], x[subscript j]) for which x[subscript i] + x[subscript j] = s is amicable. The problem here is to find numbers s for which the equation [sigma](x) = s has many solutions. From inspection of tables of known amicable pairs and their pair sums one learns that certain smooth numbers s (i.e., numbers with only small prime divisors) are good candidates. With the help of a precomputed table of [sigma](p[superscript e])-values, many solutions of the equation [sigma](x) = s were found by checking divisibility of s by the tabled [sigma]-values in a recursive way. In the set of solutions found, pairs were traced which sum up to s. From 1850 smooth numbers s satisfying 4 x 10¹¹ < s < 10¹² we found 116 new amicable pairs with this algorithm. After the submission of this paper to the Vancouver Conference Mathematics of Computation 1943-1993, the computations have been extended and yielded many more new amicable pairs. In particular, the first quadruple of amicable pairs with the same pair sum (namely 16!) was found. A list is given of 587 amicable pairs with smaller member [sic] between 2.01 x 10¹¹ and 10¹², of which 565 pairs seem to be new."
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