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 A330533 #16 Jul 13 2025 10:59:12 %S A330533 28,120,496,8128,523776,2178540,33550336,142990848,459818240, %T A330533 1379454720,1476304896,8589869056,31998395520,43861478400,66433720320, %U A330533 137438691328,704575228896,30823866178560,181742883469056,6088728021160320,14942123276641920,20158185857531904 %N A330533 Multiply-perfect numbers m whose average divisor is not an integer. %C A330533 Multiply-perfect numbers m such that A(m) = sigma(m) / tau(m) is not an integer. Corresponding values of A(m): 28/3, 45/2, 496/5, 8128/7, 98208/5, 121030/3, 33550336/13, 5957952/5, ... %C A330533 Union of A046986 and A046987. Complement of A046985 with respect to A007691. %H A330533 Amiram Eldar, <a href="/A330533/b330533.txt">Table of n, a(n) for n = 1..307</a> %t A330533 Select[Range[10^6], Divisible[(s = DivisorSigma[1, #]), #] && !Divisible[s, DivisorSigma[0, #]] &] (* _Amiram Eldar_, Dec 19 2019 *) %o A330533 (Magma) [m: m in [1..10^5] | not IsIntegral(SumOfDivisors(m) / NumberOfDivisors(m)) and IsIntegral(SumOfDivisors(m) / m)]; %Y A330533 Cf. A007691, A046985, A046986, A046987. %K A330533 nonn %O A330533 1,1 %A A330533 _Jaroslav Krizek_, Dec 17 2019