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 A354072 #21 May 12 2024 00:45:45 %S A354072 6,28,496,33550336,8589869056,137438691328,2305843008139952128, %T A354072 2658455991569831744654692615953842176, %U A354072 191561942608236107294793378084303638130997321548169216,13164036458569648337239753460458722910223472318386943117783728128 %N A354072 Perfect numbers that are the sum of the divisors of some number. %C A354072 The distinct values of A000203(A146542(n)). %C A354072 Conjecture: 8128 is the only perfect number that is not in this sequence. %H A354072 Amiram Eldar, <a href="/A354072/b354072.txt">Table of n, a(n) for n = 1..11</a> %e A354072 The perfect number 28 is in the sequence because 28 = sigma(12). %e A354072 sigma(727145809044307968) = sigma(1152771972099211264) = 2305843008139952128. %o A354072 (Magma) Set(Sort([&+Divisors(m): m in [1..10^7] | &+Divisors(&+Divisors(m)) eq 2 * &+Divisors(m)])) %Y A354072 Intersection of A000396 and A002191. %Y A354072 Cf. A000203, A146542, A354073, A354074. %K A354072 nonn %O A354072 1,1 %A A354072 _Jaroslav Krizek_, May 16 2022 %E A354072 a(8)-a(10) from _Amiram Eldar_, May 12 2024