1,1

The Jacobsthal sequence gives numbers of zeros and ones in the rows of the tree:

A001045(k) = #{i: 2^k <= i < 2^(k+1) and a(i)=0};

A001045(k+1) = #{i: 2^k <= i < 2^(k+1) and a(i)=1}.

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

Index entries for sequences related to Stern's sequences

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

.[0] . . . . . . . . . . . . . . . . . [1]

................... 1

........... 1 ............. 0

....... 1 ..... 0 ..... 1 ..... 1

..... 1 . 0 . 1 . 1 . 0 . 1 . 1 . 0

.... 1 0 1 1 0 1 1 0 1 1 0 1 1 0 1 1.

Sequence in context: A103842 A065535 A093719 this_sequence A065251 A039982 A131372

Adjacent sequences: A153775 A153776 A153777 this_sequence A153779 A153780 A153781

nonn,tabf

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jan 01 2009