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!)
A229384 Positive integer solutions y1, x1, y2, x2 to Ljunggren's equation x^2 + 1 = 2y^4. 1
1, 1, 13, 239 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

See the Wikipedia links for other references.

The only square stella octangula numbers are A007588(1) = (a(1)*a(2))^2 = 1 and A007588(169) = (a(3)*a(4))^2 = 9653449.

REFERENCES

W. Ljunggren, Zur Theorie der Gleichung x^2 + 1 = Dy^4, Avh. Norske Vid. Akad. Oslo. I. 1942 (5): 27.

LINKS

Table of n, a(n) for n=1..4.

Wikipedia, Stella octangula number

Wikipedia, Wilhelm Ljunggren

EXAMPLE

239^2 + 1 = 57122 = 2*13^4.

CROSSREFS

Cf. A007588.

Sequence in context: A134493 A051689 A000824 * A181035 A228795 A271782

Adjacent sequences:  A229381 A229382 A229383 * A229385 A229386 A229387

KEYWORD

nonn,fini,full

AUTHOR

Jonathan Sondow, Sep 30 2013

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 May 13 01:24 EDT 2021. Contains 343829 sequences. (Running on oeis4.)