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 A066860 #29 Apr 16 2025 05:25:53
%S A066860 15,20,24,95,104,207,224,287,464,1023,1199,1952,4095,4607,8036,12095,
%T A066860 15872,16895,19359,22932,23519,28799,45440,45695,54144,77375,101567,
%U A066860 102024,130304,159599,163295,223199,296207,317184,352799,522752,524160
%N A066860 The sum of the non-divisors of n (less than n) is a multiple of the sum of the divisors of n.
%H A066860 Donovan Johnson, <a href="/A066860/b066860.txt">Table of n, a(n) for n = 1..300</a>
%F A066860 a(n) = A076617(n+2). - _Alex Ratushnyak_, Jul 02 2013
%F A066860 A232324(a(n)) = A024816(a(n)) mod A000203(a(n)) = 0. - _Jaroslav Krizek_, Nov 25 2013
%e A066860 Divisors of 15 = {1, 3, 5, 15}, which sum to 24. Non-divisors of 15 less than 15 = {2, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14}, which sum to 96, a multiple of 24. So 15 is a term of the sequence.
%t A066860 f[n_] := Module[{a, b, c}, a = Divisors[n]; b = Apply[Plus, Complement[Range[1, n], a]]; c = Apply[Plus, a]; Mod[b, c] == 0]; Do[If[f[n] == True, Print[n]], {n, 3, 23519}]
%t A066860 Select[Range[3, 10000], Mod[# (# + 1)/2, DivisorSigma[1, #]] == 0 &] (* _T. D. Noe_, Nov 27 2013 *)
%Y A066860 Cf. A000203, A024816, A076617, A232324.
%K A066860 nonn
%O A066860 1,1
%A A066860 _Joseph L. Pe_, Jan 25 2002
%E A066860 More terms from _Lior Manor_, Feb 10 2002