cp's OEIS Frontend

A352810 Values taken both by sigma (A000203) and by antisigma (A024816), where sigma is the sum of divisors function and antisigma is the sum of the non-divisors of n less than n function.

%I A352810 #23 Apr 12 2022 11:34:59
%S A352810 3,20,32,54,96,132,168,217,240,252,294,338,350,464,465,582,819,1052,
%T A352810 1080,1182,1280,1476,1710,1953,2220,2484,2786,3080,3200,3402,3708,
%U A352810 4074,4404,4440,4680,4794,5250,5670,6064,6080,6576,6900,7248,7458,8000,8442,8514,8940
%N A352810 Values taken both by sigma (A000203) and by antisigma (A024816), where sigma is the sum of divisors function and antisigma is the sum of the non-divisors of n less than n function.
%C A352810 Common values attained by sigma and antisigma functions, in ascending order.
%C A352810 The asymptotic density of this sequence is 0 (according to 2nd comment of A002191).
%C A352810 The smallest integers k and m such that sigma(k) = antisigma(m) = a(n) are in A352811.
%e A352810 As sigma(31) = 1+31 = 32 and antisigma(9) = 1+2+4+5+6+7+8 = 32, then 32 is a term.
%t A352810 m = 10^4; r = Range[m]; s = DivisorSigma[1, r]; as = r*(r + 1)/2 - s; Select[Intersection[s, as], # <= m &] (* _Amiram Eldar_, Apr 05 2022 *)
%Y A352810 Intersection of A002191 and A231365.
%Y A352810 Cf. A000203, A024816, A352811.
%K A352810 nonn
%O A352810 1,1
%A A352810 _Bernard Schott_, Apr 04 2022
%E A352810 More terms from _Amiram Eldar_, Apr 05 2022