It looks like the sequences A030101 and f(x) in Euler Problem 463 are the same but I am not sure. A030101: a(n) is the number produced when n is converted to base 2, reversed and then converted back to base 10. Euler Problem 463: f(1)=1, f(3)=3, f(2n)=f(n), f(4n+1)=2f(2n+1)-f(n), f(4n+3)=3f(2n+1)+2f(n) Regards Martin M. S. Pedersen