A319898 Number of digits of 2^^n.

1, 1, 1, 1, 2, 5, 19729

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

Table of n, a(n) for n=-1..5.

Wikipedia, Knuth's up-arrow notation

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

Adjacent sequences: A319895 A319896 A319897 * A319899 A319900 A319901

Keyword

nonn,base

Author

Natan Arie Consigli, Dec 15 2018

Status

approved