OFFSET
1,3
LINKS
Lucas A. Brown, Python program.
Eric Weisstein's World of Mathematics, Rhombus.
EXAMPLE
a(1) = 0 because the 1 X 1 grid has no rhombi.
a(2) = 1 because the 2 X 2 grid has one rhombus.
a(3) = 3 because the 3 X 3 grid has 3 congruence classes of rhombi (all of which are squares) out of 6 rhombi total.
a(3) = 6 because the 4 X 4 grid has 6 congruence classes of rhombi, out of 22 rhombi total:
+---------+---------+---------+
| . . . . | . . . . | . . . . |
| . . . . | o . o . | . o . . |
| o o . . | . . . . | o . o . |
| o o . . | o . o . | . o . . |
+---------+---------+---------+
| o . . o | . . . o | . o . . |
| . . . . | . o . . | . . . o |
| . . . . | . . o . | o . . . |
| o . . o | o . . . | . . o . |
+---------+---------+---------+
CROSSREFS
KEYWORD
nonn
AUTHOR
Martin Renner, Apr 03 2012
EXTENSIONS
a(7)-a(53) from Lucas A. Brown, Feb 08 2024
STATUS
approved