-34182196

Appears in sequences

• Imaginary part of (1+2i)^n.at n=22A006496
• a(n) = 5^n*sin(2n*arctan(1/2)) or numerator of tan(2n*arctan(1/2)).at n=10A066770
• Expansion of 1/(1 - 4*x + 5*x^2).at n=21A099456