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A065856 The (2^n)-th composite number. 5

%I

%S 4,6,9,15,26,48,88,168,323,627,1225,2406,4736,9351,18504,36655,72730,

%T 144450,287147,571208,1136971,2264215,4510963,8990492,17923944,

%U 35743996,71298762,142249762,283859985,566537515,1130886504,2257704401,4507834166,9001524190

%N The (2^n)-th composite number.

%C a(n) = A002808(A000079(n)).

%H Chai Wah Wu, <a href="/A065856/b065856.txt">Table of n, a(n) for n = 0..70</a>

%F a(n)-pi(a(n))-1 = 2^n.

%e composite[1] = composite[2^0] = 4, composite[2] = composite[2^1] = 6, composite[1024] = composite[2^10] = 1225, composite[1073741824}] = composite[2^30] = 1130886504.

%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[2^n], {n, 0, 36} ]

%Y Cf. A033844, A002808, A062298, A000720, A065855.

%K nonn

%O 0,1

%A _Labos Elemer_, Nov 26 2001

%E More terms from _Robert G. Wilson v_, Nov 26 2001

%E Definition corrected by _N. J. A. Sloane_, Jun 07 2009

%E Further corrections from _Reinhard Zumkeller_, Jun 24 2009

%E a(32)-a(33) from _Chai Wah Wu_, Apr 16 2018

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Last modified February 24 09:40 EST 2020. Contains 332209 sequences. (Running on oeis4.)