A189415 Number of trapezoids on an n X n grid (or geoboard).

0, 1, 50, 490, 2618, 9519, 28432, 70796, 157912, 321161, 610482, 1082570, 1848362, 3003015, 4716792, 7204604, 10730528, 15530189, 22093410, 30723078, 42146178, 56981411, 75952240, 99685104, 129757248

Offset: 1

Author

Martin Renner, Apr 21 2011

Keywords

• nonn

Links

• Eric Weisstein's World of Mathematics, Trapezoid.
• Nathaniel Johnston, C program for computing terms.

Crossrefs

Cf. A181945, A186434, A189413, A189414, A189416, A189418.

Extensions

a(6)-a(25) from Nathaniel Johnston, Apr 25 2011