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.
%I A020887 #15 Jan 23 2020 12:49:24 %S A020887 2,4,6,6,8,10,10,12,12,14,14,16,18,18,20,20,22,22,24,24,26,26,28,28, %T A020887 30,30,30,30,32,34,34,36,36,38,38,40,40,42,42,42,42,44,44,46,46,48,48, %U A020887 50,50,52,52,54,54,56,56,58,58,60,60,60,60,62,62,64,66,66,66,66,68,68,70 %N A020887 Ordered set of a + b - c as (a,b,c) runs through all primitive Pythagorean triples with a<b<c. %C A020887 Also called "excess" of primitive Pythagorean triangles and corresponds to incircle's diameter. - _Lekraj Beedassy_, Dec 01 2003 %H A020887 Ray Chandler, <a href="/A020887/b020887.txt">Table of n, a(n) for n = 1..10000</a> %H A020887 D. McCullough, <a href="http://www.math.ou.edu/~dmccullough/teaching/pythagoras2.pdf">The Height and Excess of Pythagorean Triples</a> %F A020887 a(n) = 2*A020888(n). %Y A020887 For values ordered by hypotenuse, see A087459. %K A020887 nonn %O A020887 1,1 %A A020887 _Clark Kimberling_ %E A020887 Offset corrected to 1 by _Ray Chandler_, Jan 23 2020