cp's OEIS Frontend

A204823 Sum of divisors (A000203) of deficient numbers (A005100).

%I A204823 #11 Feb 16 2025 08:33:16
%S A204823 1,3,4,7,6,8,15,13,18,12,14,24,24,31,18,20,32,36,24,31,42,40,30,32,63,
%T A204823 48,54,48,38,60,56,42,44,84,78,72,48,57,93,72,98,54,72,80,90,60,62,96,
%U A204823 104,127,84,68,126,96,72,74,114,124,140,96,80,121,126,84,108,132
%N A204823 Sum of divisors (A000203) of deficient numbers (A005100).
%C A204823 a(n) = A000203(A005100(n)) = A005100(n) + A205099(n).
%H A204823 Harvey P. Dale, <a href="/A204823/b204823.txt">Table of n, a(n) for n = 1..1000</a>
%H A204823 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DeficientNumber.html">Deficient Number</a>
%F A204823 a(n) < 8n/3. - _Charles R Greathouse IV_, Feb 19 2013
%t A204823 sddn[n_]:=Module[{s=DivisorSigma[1,n]},If[s<2n,s,0]]; DeleteCases[ sddn/@ Range[ 100],0] (* _Harvey P. Dale_, Jan 02 2015 *)
%o A204823 (PARI) for(n=1,300,s=sigma(n);if(s<2*n,print1(s", "))) \\ _Charles R Greathouse IV_, Feb 19 2013
%Y A204823 Cf. A204822 (sum of divisors of abundant numbers), A205099 (sum of proper divisors of deficient numbers).
%K A204823 nonn
%O A204823 1,2
%A A204823 _Jaroslav Krizek_, Jan 22 2012