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 2015-11-17, 14:27 #3 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 638410 Posts I'm a bit unsure of your signs here; I think [110,1],[-249,1] might be a better basis for the lattice of (x,y) with x^3 + 15x^2y + 29xy^2 + 8y^3 == 0 mod 359 Might you be confusing the matrix-which-reduces-the-basis (which is what qflll() in Pari outputs) with the reduced basis? Code: ? M=matrix(2,2) %1 = [0 0] [0 0] ? M[1,1]=110 %2 = 110 ? M[2,1]=1 %3 = 1 ? M[2,2]=1 %4 = 1 ? M[1,2]=-249 %5 = -249 ? M %6 = [110 -249] [1 1] ? redmat=qflll(M) %7 = [9 -7] [4 -3] ? M*redmat [-6 -23] [13 -10] and indeed [-6,13] and [-23,-10] appear to have f(x,y)%359==0.