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 A294887 #14 Mar 14 2024 03:48:41
%S A294887 0,0,0,0,0,0,0,0,0,0,0,6,0,0,0,0,0,6,0,0,0,0,0,18,0,0,0,0,0,6,0,0,0,0,
%T A294887 0,36,0,0,0,20,0,6,0,0,0,0,0,42,0,0,0,0,0,24,0,28,0,0,0,68,0,0,0,0,0,
%U A294887 6,0,0,0,0,0,96,0,0,0,0,0,6,0,60,0,0,0,88,0,0,0,0,0,54,0,0,0,0,0,90,0,0,0,20,0,6,0,0,0
%N A294887 Sum of nondeficient proper divisors of n.
%C A294887 Sum of divisors n smaller than n that are nondeficient numbers (in A023196).
%H A294887 Antti Karttunen, <a href="/A294887/b294887.txt">Table of n, a(n) for n = 1..20000</a>
%H A294887 <a href="/index/Su#sums_of_divisors">Index entries for sequences related to sums of divisors</a>.
%F A294887 a(n) = Sum_{d|n, d<n} A294936(d)*d. - Typo in A-number corrected by _Antti Karttunen_, Apr 04 2022
%F A294887 a(n) + A294886(n) = A001065(n).
%e A294887 Proper divisors of 90 are 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, and 45. Of these 6, 18 and 30 are in A023196, thus a(90) = 6+18+30 = 54.
%t A294887 a[n_] := DivisorSum[n, # &, # < n && DivisorSigma[1, #] >= 2*# &]; Array[a, 100] (* _Amiram Eldar_, Mar 14 2024 *)
%o A294887 (PARI) A294887(n) = sumdiv(n, d, (d<n)*(sigma(d)>=(2*d))*d);
%Y A294887 Cf. A001065, A023196, A294927, A294936, A294886, A294888, A294889.
%K A294887 nonn
%O A294887 1,12
%A A294887 _Antti Karttunen_, Nov 14 2017