%I #21 Feb 06 2024 01:50:44
%S 0,1,50,490,2618,9519,28432,70796,157912,321161,610482,1082570,
%T 1848362,3003015,4716792,7204604,10730528,15530189,22093410,30723078,
%U 42146178,56981411,75952240,99685104,129757248
%N Number of trapezoids on an n X n grid (or geoboard).
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Trapezoid.html">Trapezoid</a>.
%H Nathaniel Johnston, <a href="/A189415/a189415.c.txt">C program for computing terms</a>.
%Y Cf. A181945, A186434, A189413, A189414, A189416, A189418.
%K nonn
%O 1,3
%A _Martin Renner_, Apr 21 2011
%E a(6)-a(25) from _Nathaniel Johnston_, Apr 25 2011