A025294 - OEIS

%I #33 Mar 04 2019 09:20:17

%S 325,425,650,725,845,850,925,1025,1105,1250,1300,1325,1445,1450,1525,

%T 1625,1690,1700,1825,1850,1885,2050,2125,2210,2225,2405,2425,2465,

%U 2525,2600,2650,2665,2725,2825,2873,2890,2900,2925,3050,3125,3145,3250,3380

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

%C A025426(a(n)) > 2. - _Reinhard Zumkeller_, Feb 26 2015

%H Robert Israel and Reinhard Zumkeller, <a href="/A025294/b025294.txt">Table of n, a(n) for n = 1..10000</a> (first 2508 terms from Robert Israel)

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>

%p   N:= 100000: # generate all entries <=N

%p SSQ:= {}: SSQ2:= {}: SSQ3:= {}:

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

%p   for b from a to floor(sqrt(N-a^2)) do

%p     n:= a^2 + b^2;

%p     if member(n,SSQ2) then SSQ3:= SSQ3 union {n}

%p     elif member(n,SSQ) then SSQ2:= SSQ2 union {n}

%p     else SSQ:= SSQ union {n}

%p     end if

%p end do end do:

%p SSQ3;  # _Robert Israel_, Jan 20 2013

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

%o (Haskell)

%o a025294 n = a025294_list !! (n-1)

%o a025294_list = filter ((> 2) . a025426) [1..]

%o -- _Reinhard Zumkeller_, Feb 26 2015

%Y Complement of A025285 relative to A007692. - _Washington Bomfim_, Oct 24 2010

%Y Cf. A025426.

%K nonn

%O 1,1

%A _David W. Wilson_