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%I #20 May 11 2024 10:11:54
%S 1,-1,-1,-1,1,1,3,3,3,1,3,3,7,1,-3,-3,-1,-1,3,3,-5,-11,-9,-9,-9,-17,
%T -17,-17,-15,-3,3,3,-7,-17,-23,-23,-21,-31,-37,-37,-37,-19,-15,-15,
%U -15,-27,-23,-23,-23,-23,-33,-33,-29,-29,-39,-39,-49,-59,-59,-59,-57,-71,-71,-71,-79,-55,-53,-53,-63,-43,-39,-39
%N a(n) = Sum_{j=1..n} Sum_{k=1..n} mu(j*k), where mu is the Moebius function A008683.
%C Conjecture: a(n) changes sign infinitely often.
%H Seiichi Manyama, <a href="/A372700/b372700.txt">Table of n, a(n) for n = 1..10000</a>
%F If n is not squarefree, a(n) = a(n-1).
%F a(n) = -1 + 2 * Sum_{k=1..n} A372706(k).
%o (PARI) a(n) = sum(j=1, n, sum(k=1, n, moebius(j*k)));
%Y Cf. A002321, A008683, A013929, A372706.
%K sign,look
%O 1,7
%A _Seiichi Manyama_, May 10 2024
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