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 A046986 #23 May 09 2024 03:25:58 %S A046986 28,496,8128,2178540,33550336,142990848,459818240,1379454720, %T A046986 8589869056,43861478400,66433720320,137438691328,704575228896, %U A046986 181742883469056,6088728021160320,14942123276641920,20158185857531904,275502900594021408,622286506811515392,2305843008139952128 %N A046986 Multiply perfect numbers that are also harmonic numbers but are not arithmetic numbers. %H A046986 Amiram Eldar, <a href="/A046986/b046986.txt">Table of n, a(n) for n = 1..207</a> %F A046986 Let s1 be the sum of divisors of k and s0 be the number of divisors of k. Then, k is a term if k | s1, s1 | (k * s0), but s1 is not divisible by s0. %e A046986 k = 2178540 is a term since s0 = d(k) = 216 and s1 = sigma(k) = 8714160, s1/s0 = 8714160/216 = 121030/3 is not an integer, and (k * s0)/s1 = (2178540 * 216)/8714160 = 54 and s1/k = 8714160/2178540 = 4 are integers. %Y A046986 In A007691 and A001599 but not in A003601. %Y A046986 Cf. A000005, A000203, A046985, A046987. %K A046986 nonn %O A046986 1,1 %A A046986 _Labos Elemer_ %E A046986 a(12)-a(17) from _Donovan Johnson_, Nov 30 2008 %E A046986 Edited and a(18)-a(21) added by _Amiram Eldar_, May 09 2024