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%I #7 Mar 10 2020 10:28:59
%S 2,1,3,5,9,7,15,17,21,17,29,27,39,25,33,51,57,37,65,55,53,47,81,67,95,
%T 59,101,85,107,41,125,129,103,79,123,123,155,95,123,145,177,75,189,
%U 157,165,115,209,167,225,131,171,193,239,147,217,229,199,161,275,147
%N a(n) = Sum_{d|n, gcd(d, n/d) = 1} (-1)^omega(n/d) * prime(d).
%F Sum_{d|n, gcd(d, n/d) = 1} a(d) = prime(n).
%t a[n_] := Sum[If[GCD[n/d, d] == 1, (-1)^PrimeNu[n/d] Prime[d], 0], {d, Divisors[n]}]; Table[a[n], {n, 1, 60}]
%o (PARI) a(n) = sumdiv(n, d, if (gcd(d, n/d) ==1, (-1)^omega(n/d) * prime(d))); \\ _Michel Marcus_, Mar 10 2020
%Y Cf. A000040, A001221, A007444, A076479, A333178.
%K nonn
%O 1,1
%A _Ilya Gutkovskiy_, Mar 10 2020
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