17555689008domain: NAppears in sequencesExpansion of 1/(2*f(x)) - 1/(4 - 2*g(x)), where f(x) = sqrt(1 - 4*x) and g(x) = sqrt(1 + 4*x).at n=19A268601a(n) = Sum_{k=0..n} (-3)^(n-k) * binomial(2*n+1,k).at n=19A387085