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A190310 Number of obtuse isosceles triangles, distinct up to congruence, on a (n X n)-grid (or geoboard). 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

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

Barile, Margherita: MathWorld -- Geoboard.

Weisstein, Eric W.: MathWorld -- Obtuse Triangle.

Weisstein, Eric W.: MathWorld -- Isosceles Triangle.

FORMULA

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

CROSSREFS

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

Sequence in context: A211538 A247799 A265702 * A046746 A058599 A238662

Adjacent sequences:  A190307 A190308 A190309 * A190311 A190312 A190313

KEYWORD

nonn

AUTHOR

Martin Renner, May 08 2011

STATUS

approved

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Last modified December 16 12:37 EST 2018. Contains 318160 sequences. (Running on oeis4.)