A020890 Ordered set of (b + c - a)/2 as (a,b,c) runs through all primitive Pythagorean triples with a < b < c.

3, 10, 12, 15, 21, 30, 35, 36, 40, 44, 52, 55, 56, 63, 65, 70, 77, 78, 85, 90, 99, 102, 105, 114, 117, 119, 126, 132, 133, 136, 143, 152, 154, 161, 165, 168, 171, 176, 182, 184, 187, 195, 198, 200, 207, 208, 210, 216, 221, 225, 230, 234, 240, 247, 253, 255, 260, 261, 270

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

From Bernard Schott, May 06 2021: (Start)

Also, ordered sides b of primitive triples (a, b, c) for integer-sided triangles where side a is the harmonic mean of the 2 other sides b and c, i.e., 2/a = 1/b + 1/c with b < a < c (A343892).

The first term appearing twice is 330 = a(71) = a(72). (End)

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A020889.

Cf. Triangles with 2/a = 1/b + 1/c: A343891 (triples), A020883 (side a), A343892 (side b), A343893 (side c), A343894 (perimeter).

Formula

a(n) = A020889(n)/2.

Extensions

Offset corrected to 1 by Ray Chandler, Jan 23 2020