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%I #5 Apr 07 2021 19:56:03
%S 1,1,1,1,0,0,0,-1,-1,-1,-2,-2,-1,-3,-2,-2,-3,-2,-1,-4,0,-2,-3,0,0,-4,
%T 4,0,-3,5,3,-4,9,2,-2,11,5,-1,15,4,0,16,10,-1,20,9,1,24,12,0,25,12,1,
%U 28,16,0,25,19,2,26,22,1,26,21,-2,28,25,0,20,24,-2,23,30,-3,10
%N a(1) = a(2) = a(3) = 1; a(n+3) = Sum_{d|n} mu(n/d) * a(d).
%t a[1] = a[2] = a[3] = 1; a[n_] := a[n] = Sum[MoebiusMu[(n - 3)/d] a[d], {d, Divisors[n - 3]}]; Table[a[n], {n, 75}]
%Y Cf. A007554, A307993, A318583, A343189, A343190.
%K sign
%O 1,11
%A _Ilya Gutkovskiy_, Apr 07 2021