OFFSET
1,2
COMMENTS
a(a(n)) = n, self-inverse permutation for the natural numbers.
LINKS
MATHEMATICA
s=Range[1000]; Do[p=Prime[n]; s[[p]]=p^2, {n, PrimePi[1000]}]; Do[p=Prime[n]; s[[p^2]]=p, {n, PrimePi[Sqrt@1000]}]; s (* Zak Seidov, Jun 29 2008 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 16 2001
STATUS
approved