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A153162 Denominators of Stern-Brocot tree hanging between 1/3 and 2/3; numerators=A153161. 2
2, 5, 5, 8, 7, 7, 8, 11, 13, 12, 9, 9, 12, 13, 11, 14, 19, 21, 18, 17, 19, 16, 11, 11, 16, 19, 17, 18, 21, 19, 14, 17, 25, 30, 27, 29, 34, 31, 23, 22, 29, 31, 26, 23, 25, 20, 13, 13, 20, 25, 23, 26, 31, 29, 22, 23, 31, 34, 29, 27, 30, 25, 17, 20, 31, 39, 36, 41, 49, 46, 35, 37 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For all coprime pairs (u,v) with 1/3 < u/v < 2/3 exists a unique k such that A153161(k)=u and a(k)=v;

a(1) = 2 and for n>1: a(n) = if A025480(n-1)<>0 and A025480(n)<>0 then a(A025480(n-1))+a(A025480(n)) else if A025480(n)=0 then a(A025480(n-1))+3 else a(n)=3+a(A025480(n-1)).

LINKS

Table of n, a(n) for n=1..72.

Index entries for sequences related to Stern's sequences

N. J. A. Sloane, Stern-Brocot or Farey Tree

CROSSREFS

A047679, A007306.

Sequence in context: A092394 A027438 A204237 * A168199 A251736 A076520

Adjacent sequences:  A153159 A153160 A153161 * A153163 A153164 A153165

KEYWORD

frac,nonn,tabf

AUTHOR

Reinhard Zumkeller, Dec 22 2008

STATUS

approved

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Last modified July 21 22:02 EDT 2019. Contains 325210 sequences. (Running on oeis4.)