A218618 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.

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

Offset: 0

Author

Antti Karttunen, Dec 03 2012

Keywords

• sign

Comments

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).

Links

• Antti Karttunen, Table of n, a(n) for n = 0..8727

Crossrefs

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

Programs

Scheme

(define (A218618 n) (* (expt -1 (A213730 n)) (A213727 (A213730 n))))

Formula

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