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A280639 Triangle read by rows: T(n,k), n>=k>=1, is the number of obtuse isosceles triangles with integral coordinates that have a bounding box of size n X k. 9
0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 2, 0, 0, 4, 0, 0, 0, 0, 0, 8, 0, 2, 2, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 12, 0, 2, 2, 2, 4, 0, 0, 0, 12, 0, 0, 0, 4, 0, 0, 0, 0, 0, 16, 0, 2, 2, 2, 2, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 0, 2, 2, 2, 2, 6, 4 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,10

LINKS

Lars Blomberg, Table of n, a(n) for n = 1..9870 (the first 140 rows)

EXAMPLE

Triangle begins:

0

0,0

0,0,0

0,0,0,4

0,2,0,0,4

0,0,0,0,0,8

0,2,2,0,0,0,8

0,0,0,0,0,0,0,12

0,2,2,2,4,0,0,0,12

0,0,0,4,0,0,0,0,0,16

0,2,2,2,2,0,0,0,0,0,16

0,0,0,0,0,0,0,0,0,0,0,20

0,2,2,2,2,6,4,4,4,0,0,0,20

-------

The obtuse angle is 'o'.

For n=4, k=4:

x...   x...   ...x   ...x

..o.   ....   .o..   ....

....   .o..   ....   ..o.

...x   ...x   x...   x...

So T(4,4)=4

-------

For n=5, k=2:

x...x   ..o..

..o..   x...x

So T(5,2)=2

CROSSREFS

Cf. A190318.

See A279415 for right isosceles triangles.

See A279418 for acute isosceles triangles.

See A279413 for all isosceles triangles.

See A279433 for all right triangles.

See A280652 for all obtuse triangles.

See A280653 for all acute triangles.

See A279432 for all triangles.

Sequence in context: A259938 A136452 A247703 * A319037 A067565 A243154

Adjacent sequences:  A280636 A280637 A280638 * A280640 A280641 A280642

KEYWORD

nonn,tabl

AUTHOR

Lars Blomberg, Feb 27 2017

STATUS

approved

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Last modified November 18 09:55 EST 2019. Contains 329261 sequences. (Running on oeis4.)