cp's OEIS Frontend

A068226 Neighbor in 2-1 direction of numbers arranged as clockwise spiral.

%I A068226 #19 Jan 08 2021 04:12:31
%S A068226 6,1,4,5,18,19,20,7,8,9,2,3,14,15,16,17,38,39,40,41,42,21,22,23,24,25,
%T A068226 10,11,12,13,32,33,34,35,36,37,66,67,68,69,70,71,72,43,44,45,46,47,48,
%U A068226 49,26,27,28,29,30,31,58,59,60,61,62,63,64,65,102,103,104,105,106,107
%N A068226 Neighbor in 2-1 direction of numbers arranged as clockwise spiral.
%C A068226 Any offset (x,y) in this spiral is a permutation of the natural numbers.
%H A068226 Peter Kagey, <a href="/A068226/b068226.txt">Table of n, a(n) for n = 1..10000</a>
%H A068226 Frank Ellermann, <a href="/A068225/a068225.html">Some EIS sequences based on a spiral of natural numbers</a>.
%H A068226 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>.
%e A068226 For example, if the spiral is oriented such that 1 is immediately to the left of 2, as shown below, then a(1) = 6 because 6 is immediately to the left of 1.
%e A068226   21--22--23--24--25--26
%e A068226   |                    |
%e A068226   20  7---8---9---10  27
%e A068226   |   |            |   |
%e A068226   19  6   1---2   11  28
%e A068226   |   |       |    |   |
%e A068226   18  5---4---3   12  29
%e A068226   |                |   |
%e A068226   17--16--15--14--13  30
%e A068226                        |
%e A068226   36--35--34--33--32--31
%Y A068226 Cf. A068225 (inverse, right), A334751 (above), A334752 (below).
%K A068226 nonn,easy
%O A068226 1,1
%A A068226 _Frank Ellermann_, Feb 22 2002