A024360 - OEIS

%I #20 Jan 08 2023 17:31:56

%S 0,0,0,1,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,

%T 1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,1,0,0,0,1,0,0,1,0,0,0,0,0,

%U 0,0,0,1,0,0,0,0,1,0,0,1,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0

%N Number of primitive Pythagorean triangles with long leg n.

%C Consider primitive Pythagorean triangles (A^2 + B^2 = C^2, (A, B) = 1, A <= B); sequence gives number of times B takes value n.

%C Number of times n occurs in A020883.

%H Ray Chandler, <a href="/A024360/b024360.txt">Table of n, a(n) for n = 1..10000</a>

%H Ron Knott, <a href="http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Pythag/pythag.html">Pythagorean Triples and Online Calculators</a>

%F a(n) = A024361(n) - A024359(n). - _Ray Chandler_, Feb 03 2020

%t A[s_] := With[{s6 = StringPadLeft[ToString[s], 6, "0"]}, Cases[Import[ "https://oeis.org/A" <> s6 <> "/b" <> s6 <> ".txt", "Table"], {_, _}][[;; 10000, 2]]];

%t A@024361 - A@024359 (* _Jean-François Alcover_, Mar 27 2020 *)

%Y Cf. A020883, A024359, A024361.

%K nonn

%O 1,420

%A _David W. Wilson_