cp's OEIS Frontend

A095119 Numbers k such that s(k) >= sigma(k), where s(k) = A095118(k) is the sum of the squares of the divisors of k which are <= sqrt(k) and sigma(k) = A000203(k) is the sum of the divisors of k.

%I A095119 #19 Jun 26 2025 14:31:39
%S A095119 1,840,900,1080,1225,1260,1440,1600,1680,1800,1848,1890,1980,2016,
%T A095119 2100,2160,2340,2400,2520,2640,2700,2772,2800,2880,2970,3024,3080,
%U A095119 3120,3136,3150,3240,3276,3300,3360,3465,3528,3600,3640,3696,3780,3900,3960,3969
%N A095119 Numbers k such that s(k) >= sigma(k), where s(k) = A095118(k) is the sum of the squares of the divisors of k which are <= sqrt(k) and sigma(k) = A000203(k) is the sum of the divisors of k.
%H A095119 Amiram Eldar, <a href="/A095119/b095119.txt">Table of n, a(n) for n = 1..10000</a>
%e A095119 840 is in the sequence because s(840) = 3070 >= 2880 = sigma(840).
%t A095119 s[n_]:=Plus@@(Select[Divisors[n], #^2<=n&]^2); Select[Range[4000], s[ # ]>=DivisorSigma[1, # ]&]
%o A095119 (PARI) isok(n) = sumdiv(n, d, if (d^2 <= n, d^2)) >= sigma(n); \\ _Michel Marcus_, Aug 13 2019
%Y A095119 Cf. A000203, A095118.
%K A095119 nonn
%O A095119 1,2
%A A095119 _Dean Hickerson_, following a suggestion of _Leroy Quet_, May 28 2004