A075615 Let P(k,X)=prod(i=1,2*k, X-1/cos(Pi*(2*i-1)/(4*k)) ) which is a polynomial with integer coefficients. Sequence gives array of coefficients for P(k,X).

1, 0, -2, 1, 0, -8, 0, 8, 1, 0, -18, 0, 48, 0, -32, 1, 0, -32, 0, 160, 0, -256, 0, 128, 1, 0, -50, 0, 400, 0, -1120, 0, 1280, 0, -512, 1, 0, -72, 0, 840, 0, -3584, 0, 6912, 0, -6144, 0, 2048, 1, 0, -98, 0, 1568, 0, -9408, 0, 26880, 0, -39424, 0, 28672, 0, -8192, 1, 0, -128, 0, 2688, 0, -21504, 0, 84480, 0, -180224, 0