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A014222 a(0) = 0; thereafter a(n+1) = 3^a(n). 9

%I

%S 0,1,3,27,7625597484987

%N a(0) = 0; thereafter a(n+1) = 3^a(n).

%C Alternative definition:

%C a(n+1) = H_4(3,n) the tetration (repeated exponentiation) of 3 times n.

%C For definition of and references concerning H_n(x,y) see A054871.

%C Next term is 12580...39387 and has 3638334640025 digits [From Shawn Ligocki (sligocki(AT)gmail.com), Oct 08 2009]

%F a(n+1) = H_4(3,n) = 3^^n;

%F a(0) = 0, a(1) = 1, a(n+1) = 3^3^...^3 (n times).

%e a(0) = H_4(3,-1)= 0;

%e a(1) = H_4(3,0) = 1;

%e a(2) = H_4(3,1) = 3;

%e a(3) = H_4(3,2) = 3^3 = 27;

%e a(4) = H_4(3,3) = 3^3^3 = 7625597484987;

%e a(5) = H_4(3,4) = 3^3^3^3 = 3^7625597484987 > 10^3638334640025.

%t NestList[3^#&,0,4] (* _Harvey P. Dale_, Apr 04 2013 *)

%Y Cf. A014221 (a(n+1) = 3^a(n), or H_4(2,n)), A081561, A114561, A266199 (H_5(3,n)).

%K nonn,easy

%O 0,3

%A _N. J. A. Sloane_.

%E Revised using hyperoperation notation by _Natan Arie' Consigli_, Jan 16 2016

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Last modified October 15 03:16 EDT 2019. Contains 328025 sequences. (Running on oeis4.)