A239581 - OEIS

A239581

Number of primitive Pythagorean triangles (x, y, z) with legs x < y < 10^n.

1, 18, 179, 1788, 17861, 178600, 1786011, 17860355, 178603639, 1786036410, 17860362941

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OFFSET

1,2

COMMENTS

A Pythagorean triangle is a right triangle with integer side lengths x, y, z forming a Pythagorean triple (x, y, z). It is called primitive, if gcd(x, y, z) = 1.

Because (x, y, z) is equivalent to (y, x, z), the total number of primitive Pythagorean triangles with legs x, y < 10^n is b(n) = 2*a(n) = 2, 36, 358, 3576, 35722, ...

LINKS

Table of n, a(n) for n=1..11.

Eric Weisstein's World of Mathematics, Pythagorean Triangle.

Eric Weisstein's World of Mathematics, Pythagorean Triple.

EXAMPLE

a(1) = 1, because the only primitive Pythagorean triangle with x < y < 10 is [3, 4, 5].

CROSSREFS

Cf. A008846, A020882, A020883, A020884, A046086, A046087, A101931, A101929, A239744, A239786.

Sequence in context: A022583 A321951 A227023 * A213350 A052507 A071910

Adjacent sequences: A239578 A239579 A239580 * A239582 A239583 A239584

KEYWORD

nonn,more

AUTHOR

Martin Renner, Mar 26 2014

EXTENSIONS

a(6)-a(11) from Giovanni Resta, Mar 27 2014

STATUS

approved