%N Self-inverse permutation of the natural numbers, induced by A137661.
%C a(a(n)) = n; A137661(a(n)) = A137661(n).
%H R. Zumkeller, <a href="/A137662/b137662.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%A _Reinhard Zumkeller_, Feb 04 2008