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%I #11 Jul 26 2022 12:46:41
%S -1,0,0,0,-1,-2,-2,-2,-2,-3,-3,-3,-4,-3,-3,-3,-3,-3,-3,-3,-2,-3,-3,-3,
%T -3,-3,-3,-3,-2,-1,-1,-1,0,1,1,1,0,1,1,1,2,3,3,3,3,2,2,2,2,2,2,2,2,2,
%U 2,2,3,2,2,2,1,1,1,1,0,1,1,1,0,1,1,1,0,0,0,0,-1,0,0,0,0,-1,-1,-1,0,1,1
%N a(n) = Sum_{i=1..n} Moebius(i)*Moebius(i+1), where Moebius(n) = A008683(n).
%H Alois P. Heinz, <a href="/A330324/b330324.txt">Table of n, a(n) for n = 1..20000</a>
%p a:= proc(n) option remember; `if`(n<1, 0,
%p a(n-1)+numtheory[mobius](n*(n+1)))
%p end:
%p seq(a(n), n=1..100); # _Alois P. Heinz_, Apr 17 2021
%t Accumulate @ Table[MoebiusMu[n] * MoebiusMu[n+1], {n, 1, 100}] (* _Amiram Eldar_, Jul 26 2022 *)
%o (PARI) a(n) = sum(i=1, n, moebius(i*(i+1))); \\ _Michel Marcus_, Jul 26 2022
%Y Partial sums of A330323.
%Y Cf. A008683.
%K sign
%O 1,6
%A _N. J. A. Sloane_, Dec 12 2019
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