|
%I #13 Oct 31 2019 13:19:40
%S 81,89,101,125,129,134,146,149,153,161,162,170,171,173,185,189,194,
%T 198,201,206,209,221,225,230,233,234,241,242,243,245,246,249,250,251,
%U 254,257,261,266,269,270,274,278,281,285,289,290,293,294,297,299,305,306
%N Numbers which can be expressed as the ordered sum of 3 squares in 4 or more different ways.
%C Subset of A124967.
%H Robert Price, <a href="/A124968/b124968.txt">Table of n, a(n) for n = 1..81953</a>
%e a(1)=81 because 81 = 6^2 + 6^2 + 3^2 = 7^2 + 4^2 + 4^2 = 8^2 + 4^2 + 1^2 = 9^2 + 0^2 + 0^2.
%e 161 = 1^2 + 4^2 + 12^2 = 2^2 + 6^2 + 11^2 = 4^2 + 8^2 + 9^2 = 5^2 + 6^2 + 10^2, so 161 is in the list.
%t Select[Range[310], Length@PowersRepresentations[#, 3, 2] >= 4 &] (* _Ray Chandler_, Oct 31 2019 *)
%o (PARI) isA124968(n)={ local(cnt=0,z2) ; for(x=0,floor(sqrt(n)), for(y=x,floor(sqrt(n-x^2)), z2=n-x^2-y^2 ; if( z2>=y^2 && issquare(z2), cnt++ ; ) ; if(cnt >=4, return(1) ) ; ) ; ) ; return(0) ; } { for(n=1,800, if( isA124968(n), print1(n,", ") ; ) ; ) ; } \\ _R. J. Mathar_
%Y Cf. A124966-A124971.
%K nonn
%O 1,1
%A _Artur Jasinski_, Nov 14 2006
%E Corrected and extended by _Ray Chandler_ and _R. J. Mathar_, Nov 29 2006
|
