OFFSET
1,2
COMMENTS
A centered hexagonal grid of size n is a grid with A003215(n-1) points forming a hexagonal lattice.
LINKS
Eric Weisstein's World of Mathematics, Hex Number.
Eric Weisstein's World of Mathematics, Acute Triangle.
Eric Weisstein's World of Mathematics, Isosceles Triangle.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Martin Renner, Apr 17 2014
EXTENSIONS
a(7) from Martin Renner, May 31 2014
a(8)-a(22) from Giovanni Resta, May 31 2014
STATUS
approved