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%I #9 Aug 20 2023 10:51:08
%S 2,6,168,16320,6710880,11453201760,80421421917312,2305843008676823040,
%T 268650182136584246132736,126765060022822827559679531520,
%U 241677817415439249618874010960062464,1858395433210885261794249658823668075069440
%N a(n) = (1/n)*Sum_{d|n} moebius(d)*2^(n^2/d).
%F a(n) = (1/n)*Sum_{d|n} moebius(n/d)*(2^n)^d.
%t a[n_] := DivisorSum[n, MoebiusMu[#] * 2^(n^2/#) &] / n; Array[a, 10] (* _Amiram Eldar_, Aug 18 2023 *)
%o (PARI) a(n)=(1/n)*sumdiv(n,d,moebius(d)*2^(n^2/d))
%Y Cf. A001037, A008683.
%K nonn
%O 1,1
%A _Paul D. Hanna_, Dec 01 2009
%E a(12) from _Amiram Eldar_, Aug 18 2023
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