354144
domain: N
Appears in sequences
- a(n) = 5^n*sin(2n*arctan(1/2)) or numerator of tan(2n*arctan(1/2)).at n=7A066770
- Largest leg in right triangle with relatively prime sides and hypotenuse 5^n.at n=7A067312
- Let (A,B)=(a(2*n),a(2*n+1)), then (A,B) is (even,odd), gcd(A,B)=1 and A^2 + B^2 = 5^n. Note: a(0)=0.at n=32A098122
- Expansion of 1/(1 - 4*x + 5*x^2).at n=15A099456
- a(1) = 1, a(2) = 2; thereafter a(2n+1) = |a(2n)^2-a(2n-1)^2|, a(2n+2) = 2*a(2n-1)*a(2n).at n=9A100686
- a(n) = abs( Im((2+i)^(2^n)) ).at n=4A185457
- Values of y such that x^2 + y^2 = 5^n with x and y coprime and 0 < x < y.at n=15A230711