This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A287247 #9 May 22 2017 12:11:35
%S A287247 300629385430,331082751976,348602203870,539890623754,552235683634,
%T A287247 556381352806,556523967562,557844696646,562012970938,569170200598,
%U A287247 569518766962,573004430386,574282506778,575462269366,576199620754,577107726658,577305647026,577419601138
%N A287247 Numbers whose sum of proper divisors is equal to 289697407994.
%C A287247 The number 289697407994 is the 47th element of A283157. That is, no even number below it has more preimages under the sum-of-proper-divisors function.
%C A287247 There are exactly 123 elements in the sequence.
%C A287247 In 2016, C. Pomerance proved that, for every e>0, the number of preimages is O_e(n^{2/3+e}).
%C A287247 Conjecture: there exists a positive real number k such that the number of preimages of an even number n is O((log n)^k).
%H A287247 Anton Mosunov, <a href="/A287247/b287247.txt">Table of n, a(n) for n = 1..123</a>
%H A287247 C. Pomerance, <a href="https://math.dartmouth.edu/~carlp/aliquot.pdf">The first function and its iterates</a>, A Celebration of the Work of R. L. Graham, S. Butler, J. Cooper, and G. Hurlbert, eds., Cambridge U. Press, to appear.
%e A287247 a(1) = 300629385430, because it is the smallest number whose sum of proper divisors is equal to 289697407994: 1 + 2 + 5 + 10 + 11 + 22 + 55 + 110 + 2732994413 + 5465988826 + 13664972065 + 27329944130 + 30062938543 + 60125877086 + 150314692715 = 289697407994.
%Y A287247 Cf. A001065, A283156, A283157, A287233, A287238, A287251, A287262.
%K A287247 fini,full,nonn
%O A287247 1,1
%A A287247 _Anton Mosunov_, May 22 2017