%I #12 May 07 2016 00:25:08
%S 1,2,3,4,5,6,7,4,6,8,5,9,8,10,2,11,3,10,11,12,13,9,12,7,13,14,1,11,13,
%T 15,9,16,14,7,16,17,15,1,16,18,7,17,19,20,1,17,18,19,9,21,3,20,10,22,
%U 4,15,21,23,5,22,23,10,21,6,22,24,25,2,14,22,25,26,3
%N Start a spiral of numbers on a hexagonal tiling, with the initial hexagon as a(1) = 1. a(n) is the smallest positive integer not equal to or previously adjacent to its neighbors.
%C This is the hexagonal analog to A260643.
%H Peter Kagey, <a href="/A272573/b272573.txt">Table of n, a(n) for n = 1..10000</a>
%H Peter Kagey, <a href="/A272573/a272573.txt">Ruby program for computing sequence</a>.
%e Illustration of a(1) through a(8) and a(13):
%e | | | | | | | | | 8 9 5
%e | | 3 | 4 3 | 4 3 | 4 3 | 4 3 | 4 3 | | 4 3 8
%e 1 | 1 2 | 1 2 | 1 2 | 5 1 2 | 5 1 2 | 5 1 2 | 5 1 2 | ... | 5 1 2 6
%e | | | | | 6 | 6 7 | 6 7 4 | | 6 7 4
%Y Cf. A047932, A260643.
%K nonn
%O 1,2
%A _Peter Kagey_, May 03 2016