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%I #15 Jan 14 2024 15:06:15
%S 1,0,0,0,0,0,0,0,0,0,0,1,0,0,1,1,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,
%T 1,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,1,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,
%U 0,0,0,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,1,0,0,0,1,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,1,1,0,0,1,0,0
%N a(n) = 1 if A342001(k) is a multiple of four, and 0 otherwise.
%C Asymptotic mean of this sequence seems to be about 0.208..., i.e., about half what it is for A368997.
%H Antti Karttunen, <a href="/A368994/b368994.txt">Table of n, a(n) for n = 1..65537</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F a(n) = A121262(A342001(n)).
%F a(n) <= A353494(n).
%F a(n) <= A368997(n) <= A358680(n).
%o (PARI)
%o A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
%o A003557(n) = (n/factorback(factorint(n)[, 1]));
%o A342001(n) = (A003415(n) / A003557(n));
%o A368994(n) = !(A342001(n)%4);
%Y Cf. A003415, A121262, A342001, A353494, A358680, A368997.
%Y Characteristic function of A368995.
%K nonn
%O 1
%A _Antti Karttunen_, Jan 14 2024
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