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A319898 Number of digits of 2^^n. 1

%I #31 Jan 11 2020 15:57:47

%S 1,1,1,1,2,5,19729

%N Number of digits of 2^^n.

%C Next term is too large to fit in the data section.

%C 2^^n is _Don Knuth_'s up arrow notation for the power tower 2^2^...^2 (n times).

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Knuth&#39;s_up-arrow_notation">Knuth's up-arrow notation</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Tetration">Tetration</a>

%e 2^^-1=0, so a(-1)=1;

%e 2^^0=1, so a(0)=1;

%e 2^^1=2, so a(1)=1;

%e 2^^2=4, so a(2)=1;

%e 2^^3=16, so a(3)=2;

%e 2^^4=65536, so a(4)=5.

%Y Equals number of digits of A014221.

%K nonn,base

%O -1,5

%A _Natan Arie Consigli_, Dec 15 2018

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Last modified April 20 22:14 EDT 2024. Contains 371848 sequences. (Running on oeis4.)