Kurt Foster on Sat, 18 Nov 2023 04:19:30 +0100


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Re: question on finding exhaustive search algorithm for a^2+b^2 = N


On Nov 17, 2023, at 7:11 PM, American Citizen wrote:

My goal is an exhaustive search of 2 squares = N algorithm

I dashed off some code which may be overkill (it absolutely clobbers the problem) but seems to get the job done. I used your example as a test.

? K=bnfinit(x^2+1);
? N=5*13*17*29*37;
? v=bnfisintnorm(K,N);
? w=vecsort(vector(#v,i,abs([polcoeff(v[i],0),polcoeff(v[i],1)])),1)
%4 = [[64, 1087], [103, 1084], [167, 1076], [191, 1072], [236, 1063], [281, 1052], [292, 1049], [359, 1028], [449, 992], [512, 961], [568, 929], [601, 908], [607, 904], [664, 863], [673, 856], [743, 796], [796, 743], [856, 673], [863, 664], [904, 607], [908, 601], [929, 568], [961, 512], [992, 449], [1028, 359], [1049, 292], [1052, 281], [1063, 236], [1072, 191], [1076, 167], [1084, 103], [1087, 64]]
?

I note that if N = a^2 + b^2 with a < b, both [a, b] and [b, a] appear on the list.