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%I #5 Dec 05 2021 06:51:06
%S 1,-2,-3,2,-5,10,-7,-2,6,18,-11,-18,-13,26,27,2,-17,-32,-19,-34,39,42,
%T -23,26,20,50,-12,-50,-29,-138,-31,-2,63,66,65,88,-37,74,75,50,-41,
%U -202,-43,-82,-90,90,-47,-34,42,-112,99,-98,-53,88,105,74,111,114,-59,370
%N a(1) = 1; a(n) = -Sum_{d|n, d < n} lpf(n/d) * a(d).
%C Dirichlet inverse of A020639.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LeastPrimeFactor.html">Least Prime Factor</a>
%t a[1] = 1; a[n_] := a[n] = -Sum[(FactorInteger[n/d][[1, 1]]) a[d], {d, Most @ Divisors[n]}]; Table[a[n], {n, 1, 60}]
%Y Cf. A020639, A349789.
%K sign
%O 1,2
%A _Ilya Gutkovskiy_, Nov 30 2021
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