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%I #21 Jan 18 2020 11:07:58
%S 8857357509,10783550414,15197873690,23620285689,25537083494,
%T 34736070369,60326914934,64139567205,73969772954,75776483145,
%U 77509981185,83968675790,93092467754,100012014465,112236593469,113606741534,116519300534,118905484334,132584489114,134889106065
%N Unitary abundant numbers k such that k + 1 is also unitary abundant.
%C Apparently most of the terms are squarefree. Up to 10^13 there are 1150 terms, for only 17 terms k either k or k + 1 is nonsquarefree, and there are no terms k such that both k and k + 1 are nonsquarefree. The first nonsquarefree term is a(32) = 285491549265.
%H Giovanni Resta, <a href="/A331412/b331412.txt">Table of n, a(n) for n = 1..1150</a> (terms below 10^13)
%e 8857357509 is a term since usigma(8857357509) = 17766604800 > 2 * 8857357509, and usigma(8857357510) = 17851083264 > 2 * 8857357510, where usigma is the sum of unitary divisors function (A034448).
%Y Cf. A034448, A034683, A292704.
%Y Analogous sequences: A096399 (regular abundant), A283418 (primitive), A318167 (bi-unitary), A327635 (infinitary), A327942 (nonunitary).
%K nonn
%O 1,1
%A _Amiram Eldar_ and _Giovanni Resta_, Jan 18 2020
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