1,13

For n >= 13 the structure looks like essentially a column of tangent circles of radius 1. The circles are centered on a straight line which is parallel to the axis "y". The structure arises from the prime numbers A000040.

Table of n, a(n) for n=1..87.

N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

Index entries for sequences related to toothpick sequences

Cf. A187210, A210838, A210841, A211000-A211003, A211010, A211011, A211021-A211023.

Sequence in context: A165024 A300402 A326166 * A157639 A010096 A230864

Adjacent sequences: A211017 A211018 A211019 * A211021 A211022 A211023

nonn

Omar E. Pol, Mar 30 2012

approved