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 A039725 N1690 #26 Jul 02 2025 16:01:56 %S A039725 6,9,10,12,15,18,20,21,24,27,28,30,33,35,36,39,40,42,44,45,48,50,51, %T A039725 52,54,56,57,60,63,66,69,70,72,75,78,80,81,84,87,88,90,93,96,98,99, %U A039725 100,102,104,105,108,110,111,112,114,117,120,123,126,129,130,132,135,136 %N A039725 Even abundant numbers divided by 2. %C A039725 While the first even abundant number is 12 = 2^2*3, the first odd abundant is 945 = 3^3*5*7, the 232nd abundant number! %C A039725 The asymptotic density of this sequence is in the interval (0.491096, 0.491156) (based on the known bounds on the densities of A005101 and A005231; see A302991 and A322287). - _Amiram Eldar_, Mar 11 2024 %D A039725 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %H A039725 T. D. Noe, <a href="/A039725/b039725.txt">Table of n, a(n) for n = 1..10000</a> %F A039725 a(n) = A173490(n) / 2. %e A039725 The first even abundant number is 12, so 12/2 = 6 is the first element in this sequence. %t A039725 Select[Range[2,300,2],DivisorSigma[1,#]>2*#&]/2 (* _Harvey P. Dale_, Mar 22 2020 *) %Y A039725 Cf. A005101, A005231, A173490, A302991, A322287. %K A039725 easy,nonn %O A039725 1,1 %A A039725 _N. J. A. Sloane_. This was included in the 1973 "Handbook", but was then dropped from the database. Resubmitted by _James Sellers_. Entry revised by _N. J. A. Sloane_, Jun 12 2012 %E A039725 Corrected and edited by _Daniel Forgues_, Nov 22 2010