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a(n) = [x^n] Product_{k=1..n} (x^(k^2) + 1 + 1/x^(k^2)).
3

%I #5 Jan 23 2024 08:41:02

%S 1,1,0,1,3,5,7,13,35,82,168,409,1035,2540,6262,16068,41474,107259,

%T 279256,736359,1953946,5205746,13938670,37567522,101675407,276158642,

%U 752927255,2060852216,5658658210,15582628517,43032891276,119166025289,330808837377

%N a(n) = [x^n] Product_{k=1..n} (x^(k^2) + 1 + 1/x^(k^2)).

%t Table[Coefficient[Product[(x^(k^2) + 1 + 1/x^(k^2)), {k, 1, n}], x, n], {n, 0, 32}]

%Y Cf. A000290, A316706, A348165, A350249.

%K nonn

%O 0,5

%A _Ilya Gutkovskiy_, Jan 23 2024