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A211670 Number of iterations (...f_4(f_3(f_2(n))))...) such that the result is < 2, where f_j(x):=x^(1/j). 7
0, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Different from A001069, but equal for n < 16.

LINKS

Table of n, a(n) for n=1..90.

FORMULA

a(2^(n!)) = a(2^((n-1)!))+1, for n>1.

G.f.: g(x)= 1/(1-x)*sum_{k=1..infinity} x^(2^(k!)). The explicit first terms of the g.f. are

g(x)=(x^2+x^4+x^64+x^16777216+...)/(1-x).

EXAMPLE

a(n)=1, 2, 3, 4, 5 for n=2^(1!), 2^(2!), 2^(3!), 2^(4!), 2^(5!) =2, 4, 64, 16777216, 16777216^5.

CROSSREFS

Cf. A001069, A010096, A084558, A211662, A211664, A211666, A211668, A211669.

Sequence in context: A138902 A211668 A255270 * A036452 A285481 A282622

Adjacent sequences:  A211667 A211668 A211669 * A211671 A211672 A211673

KEYWORD

base,nonn

AUTHOR

Hieronymus Fischer, Apr 30 2012

STATUS

approved

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Last modified December 8 14:38 EST 2019. Contains 329865 sequences. (Running on oeis4.)