The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A279415 Triangle read by rows: T(n,k), n>=k>=1, is the number of right isosceles  triangles with integral coordinates that have a bounding box of size n X k. 8
 0, 0, 4, 0, 2, 4, 0, 0, 4, 4, 0, 0, 2, 4, 4, 0, 0, 0, 4, 4, 4, 0, 0, 0, 2, 4, 4, 4, 0, 0, 0, 0, 4, 4, 4, 4, 0, 0, 0, 0, 2, 4, 4, 4, 4, 0, 0, 0, 0, 0, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 2, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 2, 4, 4 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Lars Blomberg, Table of n, a(n) for n = 1..9870 (the first 140 rows) EXAMPLE Triangle begins: 0 0,4 0,2,4 0,0,4,4 0,0,2,4,4 0,0,0,4,4,4 0,0,0,2,4,4,4 0,0,0,0,4,4,4,4 0,0,0,0,2,4,4,4,4 0,0,0,0,0,4,4,4,4,4 0,0,0,0,0,2,4,4,4,4,4 0,0,0,0,0,0,4,4,4,4,4,4 0,0,0,0,0,0,2,4,4,4,4,4,4 ------- The right angle is 'o'. For n=4, k=3: x...   .o..   ..o.   ...x ...x   ...x   x...   x... .o..   x...   ...x   ..o. So T(4,3)=4 ------- For n=4, k=4: o..x   x..o   x...   ...x ....   ....   ....   .... ....   ....   ....   .... x...   ...x   o..x   x..o So T(4,4)=4 CROSSREFS Cf. A187452. See A280639 for obtuse 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: A058997 A261164 A323982 * A201399 A145894 A021881 Adjacent sequences:  A279412 A279413 A279414 * A279416 A279417 A279418 KEYWORD nonn,tabl AUTHOR Lars Blomberg, Feb 27 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 26 14:08 EST 2020. Contains 331280 sequences. (Running on oeis4.)