%N Position of 2n in A073662.
%C It is not clear that each even number will appear in A073662, though I've checked it up to 20000.
%F a(n) = position of (2n) in A073662: A073662(a(n)) = 2n.
%e a(1)=4 because 2*1=2 appears at 4th position in A073662, a(14)=14 because 2*14=28 appears at 14th position in A073662,
%Y Cf. A073662, A073664, A076023.
%A _Zak Seidov_, Sep 30 2002