cp's OEIS Frontend

A334020 Numbers k such that s(k) = s(k+1), where s(k) is the sum of unitary divisors of k that are smaller than sqrt(k) (A334019).

%I A334020 #9 Apr 13 2020 05:44:54
%S A334020 2,3,4,7,8,16,31,127,186,256,318,434,473,574,582,588,730,735,819,978,
%T A334020 1245,1357,1374,1397,1420,1421,1500,1506,1661,1694,1902,1956,1988,
%U A334020 2059,2085,2147,2166,2329,2453,2505,2506,2534,2754,2770,2868,2954,2988,3345,3377
%N A334020 Numbers k such that s(k) = s(k+1), where s(k) is the sum of unitary divisors of k that are smaller than sqrt(k) (A334019).
%H A334020 Amiram Eldar, <a href="/A334020/b334020.txt">Table of n, a(n) for n = 1..10000</a>
%e A334020 2 is a term since A334019(2) = A334019(3) = 1.
%t A334020 s[n_] := DivisorSum[n, # &, #^2 < n && CoprimeQ[#, n/#] &]; Select[Range[3000], s[#] == s[# + 1] &]
%Y A334020 Cf. A064125, A324295, A334019,
%K A334020 nonn
%O A334020 1,1
%A A334020 _Amiram Eldar_, Apr 12 2020