%I #13 Mar 08 2016 18:30:13
%S 1,2,3,4,5,6,7,8,9,10,11,18,13,14,15,16,17,12,19,50,21,22,23,24,25,26,
%T 27,98,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,242,75,46,47,48,
%U 49,20,51,338,53,54,55,56,57,58,59,60,61,62,147,64,65,66,67,578,69,70,71
%N a(n) = if n=p*q^2 for primes p<>q then q*p^2 else n.
%C a(a(n))=n: a self-inverse permutation of natural numbers.
%H Ivan Neretin, <a href="/A072356/b072356.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%p N:= 100: # to get a(1) to a(N)
%p Ps:= select(isprime, [$1..N/2]):
%p Qs:= select(`<=`,Ps,floor(sqrt(N/2))):
%p A:= <($1..N)>:
%p for p in Ps do
%p for q in Qs do
%p if p*q^2 <= N then A[p*q^2]:= q*p^2 fi
%p od
%p od:
%p convert(A,list); # _Robert Israel_, Mar 08 2016
%t Table[If[Sort[(ar = Transpose[FactorInteger[n]])[[2]]] == {1, 2}, Times @@ (Reverse[ar[[1]]]^ar[[2]]), n], {n, 71}] (* _Ivan Neretin_, Jul 09 2015 *)
%Y Cf. A054753.
%K nonn
%O 1,2
%A _Reinhard Zumkeller_, Jul 18 2002
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