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A065607 Related to reciprocal Pythagorean triples: 1/a(n)^2 + 1/k^2 = 1/j^2 has an integer solution (k,j) with k<a(n). 5
20, 40, 60, 80, 100, 120, 140, 156, 160, 180, 200, 220, 240, 255, 260, 280, 300, 312, 320, 340, 360, 380, 400, 420, 440, 460, 468, 480, 500, 510, 520, 540, 560, 580, 600, 600, 609, 620, 624, 640, 660, 680, 700, 720, 740, 760, 765, 780, 780, 800, 820, 840 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The entries 600 and 780 occur in two solutions each; the others entries uniquely.

LINKS

Table of n, a(n) for n=0..51.

MAPLE

a := []; for n from 2 to 1000 do for m from 2 to n do if (numer(simplify(1/n^2+1/m^2))=1) then if type(sqrt(denom(simplify(1/n^2+1/m^2))), integer)=true then print(n, m, ifactor(n), ifactor(m), ifactor(denom(simplify(1/n^2+1/m^2))), sqrt(denom(simplify(1/n^2+1/m^2)))); a := [op(a), n]; fi fi od od; print(a);

CROSSREFS

Sequence in context: A046794 A104153 A049057 * A008602 A061830 A235282

Adjacent sequences:  A065604 A065605 A065606 * A065608 A065609 A065610

KEYWORD

nonn

AUTHOR

Len Smiley, Dec 01 2001

STATUS

approved

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Last modified August 18 08:57 EDT 2019. Contains 326077 sequences. (Running on oeis4.)