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A190318 Number of obtuse isosceles triangles on an n X n grid. 4
0, 0, 0, 4, 36, 100, 256, 496, 968, 1672, 2736, 4092, 6188, 8764, 12144, 16464, 22224, 28928, 37400, 47076, 59244, 73580, 90344, 109000, 132048, 158000, 187528, 220716, 259348, 301388, 350088, 402792, 463176, 529720, 602888, 683092, 774476, 872100, 978232 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
Place all bounding boxes of A280639 that will fit into the n X n grid in all possible positions, and the proper rectangles in two orientations: a(n) = Sum(i=1..n, Sum(j=1..i, k * (n-i+1) * (n-j+1) * A280639(i,j))) where k=1 when i=j and k=2 otherwise. - Lars Blomberg, Mar 02 2017
LINKS
Lars Blomberg, Table of n, a(n) for n = 1..10000 (the first 100 terms from Chai Wah Wu)
Nathaniel Johnston, C program for computing terms
FORMULA
a(n) = A186434(n) - A190317(n) - A187452(n).
CROSSREFS
Sequence in context: A152760 A361719 A016826 * A193874 A254939 A038688
KEYWORD
nonn
AUTHOR
Martin Renner, May 08 2011
EXTENSIONS
a(10)-a(39) from Nathaniel Johnston, May 09 2011
STATUS
approved

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Last modified May 22 09:32 EDT 2024. Contains 372745 sequences. (Running on oeis4.)