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 A109321 #15 Sep 22 2019 07:48:07 %S A109321 24,30,84,120,140,224,234,270,308,364,476,532,644,672,1488,1638,2480, %T A109321 3472,3724,4095,5456,5624,6200,6435,6448,8432,9424,11408,14384,15872, %U A109321 18352,20336,21328,23312,24384,26288,29264,29450,30256,33232,35150 %N A109321 Admirable numbers n such that the subtracted divisor is > sqrt(n). %C A109321 Solutions to sigma(x)=2(x+d) with d > sqrt(x) being a proper divisor of x. The subsequence A165772 contains most of the terms. - _M. F. Hasler_, Oct 11 2009 %H A109321 Amiram Eldar, <a href="/A109321/b109321.txt">Table of n, a(n) for n = 1..1200</a> %e A109321 a(2)=30 because 1+2+3+5+10+15-6 = 30 and 6 > sqrt(30) = 5.477... %t A109321 aQ[n_] := (d = DivisorSigma[1, n] - 2n) > 0 && EvenQ[d] && Mod[n, d/2] == 0 && d < 2n && d^2 > 4n; Select[Range[35150], aQ] (* _Amiram Eldar_, Sep 22 2019 *) %o A109321 (PARI) is_A109321(n)= my(d=sigma(n)-2*n); d>0 && bittest(d,0)==0 && d<2*n && d*d>4*n && 2*n%d==0 \\ _M. F. Hasler_, Oct 11 2009 %Y A109321 Cf. A111592. %K A109321 nonn %O A109321 1,1 %A A109321 _Jason Earls_, Aug 20 2005