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A084648 Hypotenuses for which there exist 4 distinct integer triangles. 19
65, 85, 130, 145, 170, 185, 195, 205, 221, 255, 260, 265, 290, 305, 340, 365, 370, 377, 390, 410, 435, 442, 445, 455, 481, 485, 493, 505, 510, 520, 530, 533, 545, 555, 565, 580, 585, 595, 610, 615, 625, 629, 663, 680, 685, 689, 697, 715, 730, 740, 745 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers whose square is decomposable in 4 different ways into the sum of two nonzero squares: these are those with exactly 2 distinct prime divisors of the form 4k+1, each with multiplicity one, or with only one prime divisor of this form with multiplicity 4. - Jean-Christophe Hervé, Nov 11 2013

LINKS

Table of n, a(n) for n=1..51.

Eric Weisstein's World of Mathematics, Pythagorean Triple

EXAMPLE

a(1) = 65 = 5*13, and 65^2 = 52^2 + 39^2 = 56^2 + 33^2 = 60^2 + 25^2 = 63^2 + 16^2. - Jean-Christophe Hervé, Nov 11 2013

MATHEMATICA

Clear[lst, f, n, i, k] f[n_]:=Module[{i=0, k=0}, Do[If[Sqrt[n^2-i^2]==IntegerPart[Sqrt[n^2-i^2]], k++ ], {i, n-1, 1, -1}]; k/2]; lst={}; Do[If[f[n]==4, AppendTo[lst, n]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 12 2009 *)

CROSSREFS

Cf. A002144, A004144, A006339, A046080, A046109.

CF. A083025, A084645, A084646, A084647, A084649.

Sequence in context: A025303 A071011 A165158 * A224770 A274044 A024409

Adjacent sequences:  A084645 A084646 A084647 * A084649 A084650 A084651

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Jun 01 2003

STATUS

approved

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Last modified July 26 08:11 EDT 2016. Contains 275042 sequences.