-21504

Appears in sequences

• Let P(k,X) = Product_{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).at n=69A075615
• Array of coefficients in Zagier's polynomials P_(n,0)(x).at n=38A075733
• a(n) = -2*a(n-1) + 4*a(n-2), a(0)=1, a(1)=2.at n=10A087205
• Hankel transform of sequence (b(n)) where b(n) = Sum_{i=0..n} binomial(2*i,i).at n=11A098106
• a(1)=1, a(2)=1, a(3)=4, a(4)=0; a(n)=12a(n-2)-16a(n-3) for n>=5.at n=9A123016
• Coefficient table for Chebyshev polynomials T(2*n,x) (increasing even powers x, without zeros).at n=39A127674
• A scaled version of the coefficient array for orthogonal polynomials defined by C(2n,n).at n=39A128412
• Riordan array ((1-2x)/(1+2x),x/(1+2x)^2).at n=39A128414
• Matrix log of triangle A111636, where A111636(n,k) = (2^k)^(n-k)*C(n,k) for n>=k>=0.at n=33A134530
• Binomial transform of [1, 2, -3, -4, 5, 6, -7, -8, 9, 10, ...].at n=20A140230
• Denominators of a series expansion for Pi/2.at n=15A156269
• Denominators of a BBP series for Pi/4.at n=10A164916
• a(n)=(-1)^n*(-2)^C(n,2)*A001045(n+1).at n=5A186196
• G.f. C(x)^(1/2) satisfies C(x)^(1/2) - S(x)^(1/2) = 1 such that C'(x)*S(x)^(1/2) = S'(x)*C(x)^(1/2) = 72*x.at n=6A299855
• Triangle read by rows: T(0,0) = 1; T(n,k) = 2*T(n-1,k) - 2*T(n-2,k-1) + T(n-3,k-2) for k = 0..floor(2*n/3); T(n,k)=0 for n or k < 0.at n=47A304213
• Binomial transform of [0, 1, 2, -3, -4, 5, 6, -7, -8, ...].at n=21A316386
• Coefficients of successive polynomials formed by iterating f(x) = -1 + 2x^2. Irregular triangle read by rows.at n=14A321369