OFFSET
1,2
COMMENTS
(1) All a(n) are square numbers. The sequence of their roots is A244507.
(2) On a j X j X j grid, j = 3n-2, the maximal number of points that can be placed is the pentagonal number A000326(n).
(3) On a maximally occupied grid, the following grid points "X" are always occupied (example for j = 7, for other j's expand this pattern):
X
. .
. . .
x . . X
. . . . .
. . . . . .
X . . X . . X
LINKS
Eric Weisstein's World of Mathematics, Maximum Independent Vertex Set
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Heinrich Ludwig, Jul 11 2014
EXTENSIONS
a(10) from Heinrich Ludwig, Aug 17 2014
STATUS
approved