A273931 - OEIS

%I #17 Jan 02 2023 12:30:52

%S 59999219280,69626138400,73605331800,89398663200,89398663200,

%T 90391981680,94320626400,94832992800,103169959200

%N Amicable 5-tuples: (x1,...,x5) such that sigma(x1)=...=sigma(x5)=x1+...+x5, x1<x2<x3<x4<x5. Sequence gives x3 numbers.

%C The 5-tuple starting with 53542288800 was given by Donovan Johnson. The common value of sigma(x) is 294821130240.

%C A larger 5-tuple, (55766707476480, 56992185169920, 57515254917120, 57754372515840, 57829096765440), was found by Michel Marcus on Dec 09 2013. The common value of sigma(x) is 285857616844800.

%C A still larger example (227491164588441600, 228507506351308800, 229862628701798400, 230878970464665600, 243752632794316800), probably the first one to be published, had been found by Yasutoshi Kohmoto in 2008, cf. link to SeqFan post.

%C Other terms from John Cerkan.

%C There are different definitions for amicable k-tuples, cf. link to MathWorld.

%H John Cerkan, <a href="/A273931/a273931.txt">More terms, with gaps.</a>

%H Yasutoshi Kohmoto, <a href="http://list.seqfan.eu/oldermail/seqfan/2008-November/000217.html">Sigma(x)=Sigma(y)=Sigma(z)=Sigma(u)=Sigma(v)=x+y+z+u+v</a>, SeqFan list, Nov 23 2008

%H Yasutoshi Kohmoto, <a href="http://list.seqfan.eu/oldermail/seqfan/2013-December/012089.html">Sigma(x)=Sigma(y)=Sigma(z)=Sigma(u)=Sigma(v)=x+y+z+u+v</a>, SeqFan list, Dec 09 2013

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AmicableTriple.html">Amicable Triple</a>.

%Y Cf. A233553, A273928, A273930, A273933, A273934, A273936 (5-tuples).

%Y Cf. A036471 - A036474 and A116148 (quadruples).

%Y Cf. A125490 - A125492 and A137231 (triples).

%K nonn,more

%O 1,1

%A _John Cerkan_, Jun 04 2016