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A125490 Amicable triples: numbers such that sigma(x) = sigma(y) = sigma(z) = x+y+z, x<y<z. We order these triples according to the common value of sigma. Sequence gives x numbers. 19
1980, 9180, 21168, 23940, 37380, 38940, 38940, 39480, 46368, 47124, 53088, 57420, 66720, 67860, 69720, 73320, 75180, 77490, 72072, 86040, 93456, 96660, 92820, 100980, 100980, 112140, 118944, 121800, 139080, 141372 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
G. Resta computed these terms.
As stated, we first order by common sigma value. When the common value of sigma is the same for several triples, these are then sorted (ascending) by the smallest member. When the smallest members also agree, we go on to the second smallest members, and so on, lexicographically. - John Cerkan, Jun 18 2016
LINKS
John Cerkan, Table of n, a(n) for n = 1..10000 [Terms 1 through 1000 were computed by Donovan Johnson]
EXAMPLE
1980 is in the sequence since sigma(1980) = sigma(2016) = sigma(2556) = 6552 = 1980 + 2016 + 2556. - Michael B. Porter, Jun 29 2016
CROSSREFS
Cf. A125491, A125492, A137231 (x+y+z).
Cf. A036471 - A036474 and A116148 (amicable quadruples).
Cf. A233553 for amicable 5-tuples.
Cf. A000203 (sigma function).
Sequence in context: A343972 A225235 A289907 * A237334 A035870 A345517
KEYWORD
nonn
AUTHOR
Yasutoshi Kohmoto, Dec 11 2006
EXTENSIONS
Definition corrected by N. J. A. Sloane, Nov 27 2008
a(13)-a(30) from Donovan Johnson, Apr 14 2010
STATUS
approved

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Last modified March 28 16:28 EDT 2024. Contains 371254 sequences. (Running on oeis4.)