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%I #15 Jul 25 2019 10:06:51
%S 1215571544,1270824975,1467511664,1512587175,1530808335,1579407344,
%T 1638031815,1727239544
%N Quasi-sociable numbers.
%C The smallest quasi-sociable number cycle is {1215571544, 1270824975, 1467511664, 1530808335, 1579407344, 1638031815, 1727239544, 151258717, 1215571544}. They are the only known quasi-sociable numbers in 2019.
%C a(9) > 10^12, if it exists. - _Giovanni Resta_, Jul 25 2019
%H David Moews, <a href="http://djm.cc/redsoc.fmtlist">Reduced sociable numbers</a> (e-mailed by Mitchell Dickerman on Sep. 10, 1997).
%e 1215571544 = 2^3 * 11 * 13813313
%e 1270824975 = 3^2 * 5^2 * 7 * 19 * 42467
%e 1467511664 = 2^4 * 19 * 599 * 8059
%e 1530808335 = 3^3 * 5 * 7 * 1619903
%e 1579407344 = 2^4 * 31^2 * 59 * 1741
%e 1638031815 = 3^4 * 5 * 7 * 521 * 1109
%e 1727239544 = 2^3 * 2671 * 80833
%e 1512587175 = 3 * 5^2 * 11 * 1833439
%Y Cf. A122726 (sociable numbers), A005276 (betrothed (or quasi-amicable) numbers).
%K nonn,hard
%O 1,1
%A _Donghwi Park_, Jul 16 2019