圆锥曲线因子分解算法

wsc810

1. B = 7; n = 45113; v = 1; u = 1; a = 2;
   
2. For[j = 1, Prime[j] <= B, j++,
   
3. p = Prime[j]; l = Floor[N[Log[B]/Log[p]]];
   
4. For[i = 1, i <= 10, i++, c = v; d = u;
   
5.   f[{s_, t_}] := Mod[{s c + a t d, s d + t c}, n];
   
6. {v, u} = Nest[f, {v, u}, p - 1]]];
   
7. GCD[u, n]

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选取整数a ,使得雅克比符号 $(a/n)=-1$, n 为要分解的数

这里的  i   怎么理解，B  怎样选取