A369729 - OEIS

%I #7 Jan 30 2024 11:42:11

%S 0,1,1,2,5,13,38,118,380,1262,4277,14745,51541,182182,650095,2338706,

%T 8472697,30884150,113189168,416839177,1541726967,5724470097,

%U 21330062502,79733319862,298922247363,1123678419818,4234465089737,15993581636893,60535561889465

%N Number of solutions to +- 1 +- 3 +- 5 +- 7 +- ... +- (4*n-3) = 1.

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

%t Table[Coefficient[Product[(x^(2 k - 1) + 1/x^(2 k - 1)), {k, 1, 2 n - 1}], x, 1], {n, 0, 27}]

%Y Cf. A005408, A063866, A156700, A292476, A367087.

%K nonn

%O 0,4

%A _Ilya Gutkovskiy_, Jan 30 2024