1917583360domain: NAppears in sequencesa(n) = 2^(n-4)*C(n,4).at n=18A003472Let P(n,X) = Product_{i=1..2n+1} (X - 1/cos(Pi*k/(2n+1))); then P(n,X) is a polynomial with integer coefficients. Sequences gives maximum values of absolute values of coefficients of P(n,X).at n=13A075581