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%I #11 May 15 2022 17:21:19
%S 0,0,0,0,1,0,0,0,0,1,0,0,1,0,0,0,1,0,0,1,0,0,0,0,0,1,0,0,1,0,0,0,0,1,
%T 0,0,1,0,0,1,1,0,0,0,1,0,0,0,0,0,0,1,1,0,0,0,0,1,0,0,1,0,0,0,0,0,0,1,
%U 0,0,0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,0,0,0,1,0,0,1,0,1,0,0,1,0,0,0,1,0,0,1,1,0,0,0,0,1,0,0,0
%N a(n) = 1 if sigma(n) is of the form 4m+2, otherwise 0.
%H Antti Karttunen, <a href="/A353812/b353812.txt">Table of n, a(n) for n = 1..100000</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F a(n) = A347870(n) - A353811(n).
%F a(n) >= A353813(n).
%t a[n_] := If[Mod[DivisorSigma[1, n], 4] == 2, 1, 0]; Array[a, 100] (* _Amiram Eldar_, May 13 2022 *)
%o (PARI) A353812(n) = (2==(sigma(n)%4));
%Y Characteristic function of A191217.
%Y Cf. A000203, A347870, A353811.
%Y Differs from A353813 for the first time at n=325, where a(325) = 1, while A353813(325) = 0.
%K nonn
%O 1
%A _Antti Karttunen_, May 13 2022
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