A218618 - OEIS

%I #10 Feb 08 2013 05:02:59

%S 0,1,-1,1,-1,3,1,-1,3,5,-1,1,-1,3,5,-1,-7,1,1,3,1,-1,3,5,-1,-7,1,1,3,

%T -7,1,1,-5,1,-5,-3,-1,1,-1,3,5,-1,-7,1,1,3,-7,1,1,-5,1,-5,-3,-1,-7,1,

%U 1,-5,1,11,1,1,13,1,-5,-1,3,1,-1,3,5,-1,-7,1,1,3

%N Absolute value of a(n) tells the size of the n-th side-tree ("tendril", A213730(n)) in the binary beanstalk; the sign tells on which side of the infinite trunk (A179016) it is.

%C Positive and negative terms correspond to the tendrils that sprout respectively at the left and right sides of the infinite trunk, when the beanstalk is drawn with the lesser numbers branching to the left. The absolute values give the sizes of those tendrils, with all nodes included: The leaves, the internal vertices as well as the root itself: A213730(n).

%H Antti Karttunen, <a href="/A218618/b218618.txt">Table of n, a(n) for n = 0..8727</a>

%F a(n) = -1^A213730(n) * A213727(A213730(n)).

%o (Scheme): (define (A218618 n) (* (expt -1 (A213730 n)) (A213727 (A213730 n))))

%Y Partial sums: A218785, A218789. Cf. also A218786, A218613.

%K sign

%O 0,6

%A _Antti Karttunen_, Dec 03 2012