cp's OEIS Frontend

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

%I A025294 #33 Mar 04 2019 09:20:17
%S A025294 325,425,650,725,845,850,925,1025,1105,1250,1300,1325,1445,1450,1525,
%T A025294 1625,1690,1700,1825,1850,1885,2050,2125,2210,2225,2405,2425,2465,
%U A025294 2525,2600,2650,2665,2725,2825,2873,2890,2900,2925,3050,3125,3145,3250,3380
%N A025294 Numbers that are the sum of 2 nonzero squares in 3 or more ways.
%C A025294 A025426(a(n)) > 2. - _Reinhard Zumkeller_, Feb 26 2015
%H A025294 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 A025294 <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%p A025294   N:= 100000: # generate all entries <=N
%p A025294 SSQ:= {}: SSQ2:= {}: SSQ3:= {}:
%p A025294 for a from 1 to floor(sqrt(N)) do
%p A025294   for b from a to floor(sqrt(N-a^2)) do
%p A025294     n:= a^2 + b^2;
%p A025294     if member(n,SSQ2) then SSQ3:= SSQ3 union {n}
%p A025294     elif member(n,SSQ) then SSQ2:= SSQ2 union {n}
%p A025294     else SSQ:= SSQ union {n}
%p A025294     end if
%p A025294 end do end do:
%p A025294 SSQ3;  # _Robert Israel_, Jan 20 2013
%t A025294 okQ[n_] := Length[Select[PowersRepresentations[n, 2, 2][[All, 1]], Positive] ] > 2; Select[Range[5000], okQ] (* _Jean-François Alcover_, Mar 04 2019 *)
%o A025294 (Haskell)
%o A025294 a025294 n = a025294_list !! (n-1)
%o A025294 a025294_list = filter ((> 2) . a025426) [1..]
%o A025294 -- _Reinhard Zumkeller_, Feb 26 2015
%Y A025294 Complement of A025285 relative to A007692. - _Washington Bomfim_, Oct 24 2010
%Y A025294 Cf. A025426.
%K A025294 nonn
%O A025294 1,1
%A A025294 _David W. Wilson_