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A319898 Number of digits of 2^^n. 1
1, 1, 1, 1, 2, 5, 19729 (list; graph; refs; listen; history; text; internal format)
OFFSET
-1,5
COMMENTS
Next term is too large to fit in the data section.
2^^n is _Don Knuth_'s up arrow notation for the power tower 2^2^...^2 (n times).
LINKS
Wikipedia, Tetration
EXAMPLE
2^^-1=0, so a(-1)=1;
2^^0=1, so a(0)=1;
2^^1=2, so a(1)=1;
2^^2=4, so a(2)=1;
2^^3=16, so a(3)=2;
2^^4=65536, so a(4)=5.
CROSSREFS
Equals number of digits of A014221.
Sequence in context: A323338 A057678 A090071 * A325957 A247148 A139062
KEYWORD
nonn,base
AUTHOR
_Natan Arie Consigli_, Dec 15 2018
STATUS
approved

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Last modified March 5 03:04 EST 2024. Contains 370537 sequences. (Running on oeis4.)