login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A281877 Numbers that are a primitive sum of two squares in more than 2 ways. 3
1105, 1885, 2210, 2405, 2465, 2665, 3145, 3445, 3485, 3770, 3965, 4505, 4745, 4810, 4930, 5185, 5330, 5365, 5525, 5785, 5945, 6205, 6290, 6305, 6409, 6565, 6890, 6970, 7085, 7345, 7565, 7585, 7685, 7930, 8177, 8245, 8585, 8845, 8905, 9010, 9061, 9265, 9425, 9490, 9605, 9685, 9805 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

"Primitive" means that x and y are coprime in the representations x^2+y^2.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

N:= 10^4: # to get all terms <= N

V:= Vector(N):

for a from 1 to floor(sqrt(N)) do

  for b from 1 to min(a, floor(sqrt(N-a^2))) do

    if igcd(a, b) > 1 then next fi;

    r:= a^2 + b^2;

    V[r]:= V[r]+1;

od od:

select(n -> V[n] > 2, [$1..N]); # Robert Israel, Feb 07 2017

CROSSREFS

Cf. A224450 (exactly 1 way), A224770 (exactly 2 ways), A008784, A097102.

Sequence in context: A025305 A052155 A097102 * A159781 A264498 A102924

Adjacent sequences:  A281874 A281875 A281876 * A281878 A281879 A281880

KEYWORD

nonn

AUTHOR

R. J. Mathar, Feb 01 2017

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 November 18 02:07 EST 2019. Contains 329242 sequences. (Running on oeis4.)