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a(n) = 3^n mod n^2.
(PARI) a(n) = lift(Mod(3, n^2)^n); \\ Michel Marcus, May 05 2021
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for n in range(1, 100): print (str(3**n % n**2)+, end=', ', )
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Table[PowerMod[3, n, n^2], {n, 100}] (* Harvey P. Dale, Aug 27 2019 *)
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Alois P. Heinz, <a href="/A233471/b233471.txt">Table of n, a(n) for n = 1..10000</a>
a:= n-> 3&^n mod n^2:
seq(a(n), n=1..60); # Alois P. Heinz, Dec 22 2013
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