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 A143277 G.f.: Product_{k>0} (1 - x^(3*k))^2 / (1 - x^(3*k - 2)). 0

%I

%S 1,1,1,-1,0,0,-1,-2,-1,1,-1,-2,0,0,-1,0,2,1,-2,0,1,1,1,2,0,1,1,-1,-1,

%T 2,3,-1,0,2,-1,-1,1,1,-3,0,0,-1,1,2,0,-3,-1,-2,-2,1,0,-1,0,0,-2,0,2,

%U -2,-1,0,-2,-2,1,1,-1,2,0,-2,1,2,-1,0,3,-2,-1,2,-1,-3,3,2,-1,3,5,-1,-2,1,0,0,1,-1,0,2,0,0,3,1,-2,0,0,0,4,2,-3,1,1

%N G.f.: Product_{k>0} (1 - x^(3*k))^2 / (1 - x^(3*k - 2)).

%F Euler transform of period 3 sequence [ 1, 0, -2, ...].

%e 1 + q + q^2 - q^3 - q^6 - 2*q^7 - q^8 + q^9 - q^10 - 2*q^11 - q^14 + ...

%o (PARI) {a(n) = if( n<0, 0, polcoeff( prod(k=1, n, (1 - x^k)^([2, -1, 0][k%3 + 1]), 1 + x * O(x^n)), n))}

%K sign

%O 0,8

%A _Michael Somos_, Aug 04 2008

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Last modified April 3 17:03 EDT 2020. Contains 333197 sequences. (Running on oeis4.)