References to A080908

a(n) = the sign of r(n), where r(n) is the integer in [ -2n,2n] which is congruent to (2n)! modulo 4n+1
0, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1,

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