-98248054847domain: ZAppears in sequencesa(n) = 5^n*cos(2*n*arctan(1/2)) or denominator of tan(2*n*arctan(1/2)).at n=16A066771Real part of (1 + 2i)^(2^n) where i is sqrt(-1).at n=5A120905Real part of (4 + 3i)^n.at n=16A139030