cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

Original entry on oeis.org

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

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Author

Clark Kimberling

Keywords

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

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
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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