A025294 Numbers that are the sum of 2 nonzero squares in 3 or more ways.

325, 425, 650, 725, 845, 850, 925, 1025, 1105, 1250, 1300, 1325, 1445, 1450, 1525, 1625, 1690, 1700, 1825, 1850, 1885, 2050, 2125, 2210, 2225, 2405, 2425, 2465, 2525, 2600, 2650, 2665, 2725, 2825, 2873, 2890, 2900, 2925, 3050, 3125, 3145, 3250, 3380

Offset

1,1

Comments

A025426(a(n)) > 2. - Reinhard Zumkeller, Feb 26 2015

Links

Robert Israel and Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 (first 2508 terms from Robert Israel)

Index entries for sequences related to sums of squares

Maple

  N:= 100000: # generate all entries <=N
SSQ:= {}: SSQ2:= {}: SSQ3:= {}:
for a from 1 to floor(sqrt(N)) do
  for b from a to floor(sqrt(N-a^2)) do
    n:= a^2 + b^2;
    if member(n, SSQ2) then SSQ3:= SSQ3 union {n}
    elif member(n, SSQ) then SSQ2:= SSQ2 union {n}
    else SSQ:= SSQ union {n}
    end if
end do end do:
SSQ3;  # Robert Israel, Jan 20 2013

Mathematica

okQ[n_] := Length[Select[PowersRepresentations[n, 2, 2][[All, 1]], Positive] ] > 2; Select[Range[5000], okQ] (* Jean-François Alcover, Mar 04 2019 *)

Prog

(Haskell)
a025294 n = a025294_list !! (n-1)
a025294_list = filter ((> 2) . a025426) [1..]
-- Reinhard Zumkeller, Feb 26 2015

Crossrefs

Complement of A025285 relative to A007692. - Washington Bomfim, Oct 24 2010

Cf. A025426.

Sequence in context: A159844 A000443 A097101 * A025313 A025286 A025304

Adjacent sequences: A025291 A025292 A025293 * A025295 A025296 A025297

Keyword

nonn

Author

David W. Wilson

Status

approved