%N Exchange adjacent nonprimes and primes.
%C If we have consecutive numbers, one prime and one nonprime, swap them. So after the initial 2,1,4,3,6,5,8,7 we have "if n is prime, a(n) = n-1; if n+1 is prime, a(n) = n+1, otherwise a(n) = n".
%Y Cf. A014681
%A _Giovanni Teofilatto_, Nov 03 2009
%E Edited by Franklin T. Adams-Watters, Nov 04 2009