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%I #20 Dec 14 2016 13:20:47
%S 1,1,1,1,1,1,2,1,2,1,4,1,2,2,1,1,1,2,6,1,2,4,10,1,4,2,6,2,3,1,4,1,4,1,
%T 2,2,6,6,2,1,4,2,3,4,2,10,11,1,6,4,1,2,12,6,4,2,6,3,28,1,4,4,2,1,2,4,
%U 10,1,10,2,12,2,6,6,4,6,4,2,12,1,18,4,20,2,1,3
%N Eventual period of 2^(2^k) mod n.
%C In other words, eventual period of 2 under the map x -> x^2 mod n.
%C a(n) is a divisor of A256608(n).
%H Ivan Neretin, <a href="/A256607/b256607.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A007733(A007733(n)).
%e For n=9 the map acts as follows: 2 -> 4 -> 7 -> 4 -> 7 and so on. This means the eventual period is 2, hence a(9)=2.
%o (Haskell)
%o a256607 = a007733 . fromIntegral . a007733
%o -- _Reinhard Zumkeller_, Apr 13 2015
%Y Cf. A001146, A007733, A002326.
%Y First differs from A256608 at n=43.
%Y Column 2 of triangle in A279185.
%K nonn
%O 1,7
%A _Ivan Neretin_, Apr 04 2015
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