login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A094807 Numbers n such that primitive solutions for 1/n^2 = 1/x^2 + 1/y^2 exist. 1
12, 60, 120, 168, 360, 420, 660, 1008, 1092, 1260, 1680, 1848, 1980, 2448, 2640, 2772, 3120, 3420, 3432, 4620, 4680, 5148, 5460, 6072, 7140, 7800, 8160, 8580, 9240, 9828, 10032, 11220, 11628, 12180, 13260, 14280, 14880, 15708, 15912, 15960, 17940 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n that are the product of two legs of a primitive Pythagorean triangle, that is, n = 2xy(x^2-y^2) where x and y are two relatively prime positive integers of different parity and x is greater than y.

Numbers n which are the length of the altitude on the hypotenuse of a Pythagorean triangle and the smallest in its similarity class.

REFERENCES

E. Bahier, Recherche Methodique et Proprietes des Triangles Rectangles en Nombres Entiers, Hermann, Paris, 1916. p. 68.

LINKS

Table of n, a(n) for n=1..41.

FORMULA

Equals 2*A024365(n).

EXAMPLE

12 is in the sequence because we have 1/12^2 = 1/15^2 + 1/20^2 and gcd(12,15,20)=1.

CROSSREFS

Sequence in context: A012406 A097191 A273691 * A120644 A099829 A099830

Adjacent sequences:  A094804 A094805 A094806 * A094808 A094809 A094810

KEYWORD

nonn

AUTHOR

Lekraj Beedassy, Jun 11 2004

EXTENSIONS

Comments provided by Michael Somos, Oct 01 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 17:51 EDT 2020. Contains 333103 sequences. (Running on oeis4.)