OFFSET
0,2
COMMENTS
Also spiral constructed on the infinite hexagonal grid in which each term is the least positive integer such that no diagonal of successive adjacent cells contains a repeated term. Every number is located in the center of a hexagonal cell. Every cell is also the center of three diagonals of successive adjacent cells.
FORMULA
a(n) = A274820(n) + 1.
EXAMPLE
Illustration of initial terms as a spiral:
.
. 10 - 5 - 3 - 9 - 8
. / \
. 9 4 - 7 - 8 - 6 10
. / / \ \
. 3 1 6 - 4 - 5 7 2
. / / / \ \ \
. 11 7 4 2 - 3 1 5 9
. / / / / \ \ \ \
. 12 6 5 3 1 - 2 4 8 7
. \ \ \ \ / / /
. 9 8 6 2 - 3 - 1 7 4
. \ \ \ / /
. 10 1 4 - 5 - 7 - 6 2
. \ \ /
. 11 7 - 8 - 6 - 5 - 9
. \
. 13 - 4 - 9 - 10 - 8
.
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Jul 09 2016
STATUS
approved