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A159944 Number of different deltoids (including squares) whose vertices are on an n X n grid. 1
0, 1, 4, 11, 26, 46, 84, 123, 194, 268, 378, 478, 657, 800, 1019, 1239, 1548, 1793, 2197, 2505, 3003, 3434, 3991, 4444, 5223, 5801, 6582, 7292, 8274, 9006, 10199, 11034, 12330, 13398, 14744, 15912, 17705, 18906, 20586 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Only convex kites (A189417) are counted, not concave kites (A173502), distinct up to congruence.

LINKS

Table of n, a(n) for n=1..39.

Nathaniel Johnston, C program for computing terms

EXAMPLE

a(1) = 0, since there is only one point on a 1 X 1 grid.

a(2) = 1, since the four points on a 2 X 2 grid build a 1 X 1 square.

a(3) = 4 since there are 3 sizes of squares on a 3 X 3 grid -- 1 X 1, 2 X 2, sqrt(2) X sqrt(2) -- and a single nonsquare deltoid.

CROSSREFS

Cf. A189417, A173502.

Sequence in context: A140897 A008263 A297149 * A002763 A077270 A076048

Adjacent sequences:  A159941 A159942 A159943 * A159945 A159946 A159947

KEYWORD

nonn

AUTHOR

Demacek Ondrej (demacek(AT)gjh.sk), Apr 27 2009

EXTENSIONS

Edited by Ray Chandler, May 01 2011

Corrected and extended by Nathaniel Johnston with help from Ray Chandler, May 11 2011

STATUS

approved

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Last modified July 5 14:33 EDT 2020. Contains 335472 sequences. (Running on oeis4.)