A190309 Number of acute isosceles triangles, distinct up to congruence, on an n X n grid (or geoboard).

0, 0, 2, 5, 11, 19, 29, 40, 58, 74, 94, 113, 141, 168, 201, 227, 267, 304, 348, 390, 438, 483, 537, 590, 657, 709, 776, 837, 913, 979, 1057, 1130, 1225, 1299, 1396, 1472, 1576, 1663, 1768, 1863, 1974

Offset: 1

Author

Martin Renner, May 08 2011

Keywords

• nonn

Links

• Eric Weisstein's World of Mathematics, Geoboard.
• Eric Weisstein's World of Mathematics, Acute Triangle.
• Eric Weisstein's World of Mathematics, Isosceles Triangle.

Crossrefs

Cf. A028419, A108279, A189978, A190021, A190310.

Formula

a(n) = A189978(n) - A190310(n) - A108279(n).