A084649 Hypotenuses for which there exist exactly 5 distinct Pythagorean triangles.

3125, 6250, 9375, 12500, 18750, 21875, 25000, 28125, 34375, 37500, 43750, 50000, 56250, 59375, 65625, 68750, 71875, 75000, 84375, 87500, 96875, 100000, 103125, 112500, 118750, 131250, 134375, 137500, 143750, 146875, 150000, 153125

Offset

1,1

Comments

Numbers whose square is decomposable in 5 different ways into the sum of two nonzero squares: these are those with exactly one prime divisor of the form 4k+1 with multiplicity 5. - Jean-Christophe Hervé, Nov 12 2013

Links

Ray Chandler, Table of n, a(n) for n = 1..10000 (first 1019 terms from Jean-Christophe Hervé)

Eric Weisstein's World of Mathematics, Pythagorean Triple

Formula

Terms are obtained by the products A004144(k)*A002144(p)^5 for k, p > 0 ordered by increasing values. - Jean-Christophe Hervé, Nov 12 2013

Example

a(1) = 5^5, a(5) = 6*5^5, a(65) = 13^5. - Jean-Christophe Hervé, Nov 12 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]==5, AppendTo[lst, n]], {n, 3*6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 12 2009 *)

Crossrefs

Cf. A002144, A006339, A046080, A046109, A083025.

Cf. A004144 (0), A084645 (1), A084646 (2), A084647 (3), A084648 (4), A097219 (6), A097101 (7), A290499 (8), A290500 (9), A097225 (10), A290501 (11), A097226 (12), A097102 (13), A290502 (14), A290503 (15), A097238 (16), A097239 (17), A290504 (18), A290505 (19), A097103 (22), A097244 (31), A097245 (37), A097282 (40), A097626 (67).

Sequence in context: A102709 A057067 A223184 * A169754 A016817 A115791

Adjacent sequences: A084646 A084647 A084648 * A084650 A084651 A084652

Keyword

nonn

Author

Eric W. Weisstein, Jun 01 2003

Status

approved