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A171163 Number of children at height n in a doubly logarithmic tree. Leaves are at height 0. 1
0, 2, 2, 4, 16, 256, 65536, 4294967296, 18446744073709551616, 340282366920938463463374607431768211456, 115792089237316195423570985008687907853269984665640564039457584007913129639936 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

REFERENCES

Omer Berkman, Baruch Schieber and Uzi Vishkin (1993), "Optimal doubly logarithmic parallel algorithms based on finding all nearest smaller values", Journal of Algorithms, 14(2001)(3): 344-370

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..13

FORMULA

a(0)=0, a(1)=2; for n>1, a(n) = 2^(2^(n-2)).

MATHEMATICA

Join[{0, 2}, Table[2^2^(n-2), {n, 2, 9}]] (* Harvey P. Dale, Feb 01 2014 *)

PROG

(Python)

def doubly_log_tree_children(n):

...if(n==0):

......return 0

...if(n==1):

......return 2

...return 2**(2**(n-2))

CROSSREFS

Equals A001146 with the prefix 0, 2.

Cf. A165420. [R. J. Mathar, Dec 11 2009]

Sequence in context: A168088 A168089 A165420 * A129614 A070283 A070282

Adjacent sequences:  A171160 A171161 A171162 * A171164 A171165 A171166

KEYWORD

nonn

AUTHOR

Chad Brewbaker, Dec 04 2009

EXTENSIONS

More terms from Harvey P. Dale, Feb 01 2014

STATUS

approved

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Last modified February 16 15:17 EST 2020. Contains 331961 sequences. (Running on oeis4.)