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%I #5 Apr 07 2021 19:56:09
%S 1,1,1,1,1,0,0,0,0,-1,-1,-1,-1,-2,-2,-1,-2,-2,-3,-1,-3,-1,-4,0,-3,0,
%T -5,2,-4,1,-5,4,-5,6,-6,5,-4,8,-6,8,-5,11,-5,10,-6,17,-6,11,-3,21,-7,
%U 12,-3,26,-5,12,-4,33,-4,11,-1,37,-5,11,-2,42,-1,7,-1,48,-2,1,3,58,-3
%N a(1) = ... = a(4) = 1; a(n+4) = Sum_{d|n} mu(n/d) * a(d).
%t a[1] = a[2] = a[3] = a[4] = 1; a[n_] := a[n] = Sum[MoebiusMu[(n - 4)/d] a[d], {d, Divisors[n - 4]}]; Table[a[n], {n, 75}]
%Y Cf. A007554, A307994, A318583, A343188, A343190.
%K sign
%O 1,14
%A _Ilya Gutkovskiy_, Apr 07 2021