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The (3^n)-th composite number.
1

%I #5 Apr 21 2018 21:00:26

%S 4,8,16,40,111,306,882,2563,7513,22170,65602,194695,578949,1724117,

%T 5140568,15340177,45811041,136886318,409221920,1223856725,3661401440,

%U 10956876415,32796782398,98189738332,294021666926,880564233896

%N The (3^n)-th composite number.

%H Chai Wah Wu, <a href="/A065605/b065605.txt">Table of n, a(n) for n = 0..40</a>

%t Composite[n_Integer] := Block[ {k = n + PrimePi[n] + 1 }, While[ k != n + PrimePi[k] + 1, k = n + PrimePi[k] + 1]; Return[ k ]]; Table[ Composite[3^n], {n, 0, 25} ]

%K nonn

%O 0,1

%A _Robert G. Wilson v_, Nov 27 2001