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

1,3

Links

Table of n, a(n) for n=1..41.

Eric Weisstein's World of Mathematics, Geoboard.

Eric Weisstein's World of Mathematics, Acute Triangle.

Eric Weisstein's World of Mathematics, Isosceles Triangle.

Formula

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

Crossrefs

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

Sequence in context: A040147 A152471 A088796 * A161550 A245207 A215762

Adjacent sequences: A190306 A190307 A190308 * A190310 A190311 A190312

Keyword

nonn

Author

Martin Renner, May 08 2011

Status

approved