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%I #12 Oct 21 2023 05:33:53
%S 1,-2,0,4,4,0,8,-8,0,-8,16,0,20,-16,0,16,28,0,32,16,0,-32,40,0,16,-40,
%T 0,32,52,0,56,-32,0,-56,32,0,68,-64,0,-32,76,0,80,64,0,-80,88,0,64,
%U -32,0,80,100,0,64,-64,0,-104,112,0,116,-112,0,64,80,0,128,112
%N Totally multiplicative sequence with a(p) = 2*(p-3) for prime p.
%H G. C. Greubel, <a href="/A167312/b167312.txt">Table of n, a(n) for n = 1..1000</a>
%F Multiplicative with a(p^e) = (2*(p-3))^e. If n = Product p(k)^e(k) then a(n) = Product (2*(p(k)-3))^e(k).
%F a(3k) = 0 for k >= 1.
%F a(n) = A061142(n) * A166589(n) = 2^bigomega(n) * A166589(n) = 2^A001222(n) * A166589(n).
%t a[1] = 1; a[n_] := (fi = FactorInteger[n]; Times @@ ((fi[[All, 1]] - 3)^fi[[All, 2]])); Table[a[n]*2^PrimeOmega[n], {n, 1, 100}] (* _G. C. Greubel_, Jun 08 2016 *)
%t f[p_, e_] := (2*(p-3))^e; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, Oct 21 2023 *)
%Y Cf. A001222, A061142, A166589.
%K sign,easy,mult
%O 1,2
%A _Jaroslav Krizek_, Nov 01 2009