A190310 Number of obtuse isosceles triangles, distinct up to congruence, on an n X n grid (or geoboard).

0, 0, 0, 1, 3, 5, 9, 12, 19, 24, 32, 37, 51, 57, 69, 80, 99, 107, 127, 136, 161, 176, 196, 207, 246, 262, 286, 306, 343, 357, 399, 414, 460, 485, 517, 544, 605, 623, 659, 689, 757

Offset

1,5

Links

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

Eric Weisstein's World of Mathematics, Geoboard.

Eric Weisstein's World of Mathematics, Obtuse Triangle.

Eric Weisstein's World of Mathematics, Isosceles Triangle.

Formula

a(n) = A189978(n) - A190309(n) - A108279(n).

Crossrefs

Cf. A028419, A108279, A189978, A190022, A190309.

Sequence in context: A368613 A247799 A265702 * A046746 A344715 A058599

Adjacent sequences: A190307 A190308 A190309 * A190311 A190312 A190313

Keyword

nonn

Author

Martin Renner, May 08 2011

Status

approved