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!)
A237351 Positive integers k such that x^2 - 5xy + y^2 + k = 0 has integer solutions. 11
3, 5, 12, 17, 20, 21, 27, 35, 41, 45, 47, 48, 59, 68, 75, 80, 83, 84, 89, 101, 108, 111, 119, 125, 129, 131, 140, 147, 153, 164, 167, 173, 180, 185, 188, 189, 192, 201, 215, 227, 236, 237, 243, 245, 251, 255, 257, 269, 272, 287, 293, 300, 311, 315, 320, 327 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See comments on method used in A084917.

The equivalent sequence for x^2 - 3xy + y^2 + k = 0 is A031363.

The equivalent sequence for x^2 - 4xy + y^2 + k = 0 is A084917.

LINKS

Table of n, a(n) for n=1..56.

N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)

EXAMPLE

12 is in the sequence because x^2 - 5xy + y^2 + 12 = 0 has integer solutions, for example (x, y) = (2, 8).

CROSSREFS

Cf. A004253 (k = 3), A237254 (k = 5), A237255 (k = 17).

Cf. A031363, A084917.

For primes see A141160.

Sequence in context: A032438 A025083 A203150 * A299490 A126471 A317100

Adjacent sequences:  A237348 A237349 A237350 * A237352 A237353 A237354

KEYWORD

nonn

AUTHOR

Colin Barker, Feb 06 2014

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 June 18 03:46 EDT 2021. Contains 345098 sequences. (Running on oeis4.)