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 A239618 Number of primitive Euler bricks with side length a < b < c < 10^n, i.e., in a boxed parameter space with dimension 10^n. 1
 0, 0, 5, 19, 65, 242, 704, 1884 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS An Euler brick is a cuboid of integer side dimensions a, b, c such that the face diagonals are integers. It is called primitive if gcd(a,b,c)=1. Because the sides of a cuboid are permutable without changing its shape, the total number of primitive Euler bricks in the parameter space a, b, c < 10^n is b(n) = 6*a(n) = 0, 0, 30, 114, 390, ... LINKS Eric Weisstein's World of Mathematics, Euler Brick EXAMPLE a(3) = 5, since there are the five primitive Euler bricks [44, 117, 240], [85, 132, 720], [140, 480, 693], [160, 231, 792], [240, 252, 275] with longest side length < 1000. CROSSREFS Cf. A031173, A031174, A031175, A239620. Sequence in context: A025568 A001047 A099448 * A124806 A059509 A137745 Adjacent sequences:  A239615 A239616 A239617 * A239619 A239620 A239621 KEYWORD nonn,more AUTHOR Martin Renner, Mar 22 2014 EXTENSIONS a(6)-a(8) from Giovanni Resta, Mar 22 2014 STATUS approved

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Last modified May 29 03:06 EDT 2020. Contains 334696 sequences. (Running on oeis4.)