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A181945 Number of trapezoids, distinct up to congruence, on an (n X n)-grid (or geoboard). 0
0, 1, 9, 43, 141, 343 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..6.

Weisstein, Eric W.: MathWorld -- Trapezoid.

CROSSREFS

Cf. A181944, A189415.

Sequence in context: A195975 A185918 A116015 * A244869 A259181 A281773

Adjacent sequences:  A181942 A181943 A181944 * A181946 A181947 A181948

KEYWORD

nonn

AUTHOR

Martin Renner, Apr 03 2012

STATUS

approved

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Last modified December 14 07:15 EST 2018. Contains 318090 sequences. (Running on oeis4.)