7930904576domain: NAppears in sequencesa(n) = 2*a(n-1) + 4*a(n-2), a(0)=1, a(1)=1.at n=20A084057a(n) = 4^n * T(n,3/2) where T is the Chebyshev polynomial of the first kind.at n=10A099140Hankel transform of A128057.at n=20A128056Duplicate of A084057.at n=19A163302