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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

Adjacent sequences:  A125487 A125488 A125489 * A125491 A125492 A125493

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 September 26 08:28 EDT 2022. Contains 356993 sequences. (Running on oeis4.)