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A014222 a(0) = 0; thereafter a(n+1) = 3^a(n). 7
0, 1, 3, 27, 7625597484987 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Alternative definition:

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

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

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

LINKS

Table of n, a(n) for n=0..4.

FORMULA

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

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

EXAMPLE

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

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

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

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

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

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

MATHEMATICA

NestList[3^#&, 0, 4] (* Harvey P. Dale, Apr 04 2013 *)

CROSSREFS

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

Sequence in context: A068221 A068222 A055777 * A071107 A162414 A188927

Adjacent sequences:  A014219 A014220 A014221 * A014223 A014224 A014225

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Revised using hyperoperation notation by Natan Arie' Consigli, Jan 16 2016

STATUS

approved

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Last modified July 25 04:48 EDT 2017. Contains 289779 sequences.