The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A120090

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A120090

Numbers whose square is the perimeter of a primitive Pythagorean triangle.
(history; published version)

#17 by Peter Luschny at Fri May 24 08:42:41 EDT 2024

STATUS

reviewed

approved

#16 by Stefano Spezia at Fri May 24 08:10:10 EDT 2024

STATUS

proposed

reviewed

#15 by Jean-François Alcover at Fri May 24 07:52:07 EDT 2024

STATUS

editing

proposed

#14 by Jean-François Alcover at Fri May 24 07:52:01 EDT 2024

MATHEMATICA

isA024364[an_] := Module[{r, s}, For[ r = Floor[(an/4)^(1/2)], r <= Floor[(an/2)^(1/2)], r++, For[s = r - 1, s >= 1, s -= 2, If[2 r (r + s) == an && GCD[r, s] < 2, Return[True]]; If[2 r (r + s) < an, Break[]]]]; Return[False]];

Select[Range[2, 2000], If[isA024364[#^2], Print[#]; True, False]&] (* Jean-François Alcover, May 24 2024, after R. J. Mathar *)

STATUS

approved

editing

#13 by N. J. A. Sloane at Mon Feb 11 22:02:04 EST 2019

STATUS

proposed

approved

#12 by Charlie Neder at Mon Feb 11 21:20:30 EST 2019

STATUS

editing

proposed

#11 by Charlie Neder at Mon Feb 11 21:20:24 EST 2019

LINKS

Charlie Neder, <a href="/A120090/b120090.txt">Table of n, a(n) for n = 1..1000</a>

STATUS

approved

editing

#10 by Ray Chandler at Mon Aug 21 16:04:26 EDT 2017

STATUS

editing

approved

#9 by Ray Chandler at Mon Aug 21 16:04:22 EDT 2017

LINKS

P. Yiu, <a href="http://www.math.fau.edu/yiu/RecreationalMathematics2003.pdf">"Primitive Pythagorean triangles with square perimeters" in 'Recreational Mathematics' Chap. 6.2 pp. 50, /360</a>

STATUS

approved

editing

#8 by Jon E. Schoenfield at Sun Aug 09 15:25:38 EDT 2015

STATUS

editing

approved