groebner基计算时，含有a1，a2,a3,...,an个自变量的非线性方程组问题化简问题

lhrman

a1*a2+2*a1*a3+a2*a3=0
a1^2+a1*a2+a2^2+a2*a3+a3^2=1/4;
6 X1 v% l8 n2 Y/ t+ Q( fa1+a2+a3=1
) N4 c6 E( Z6 x9 ~; u用with（Groebner）；
! G* b5 @) U5 k/ x; p然后输入
! ^8 t( d+ I; p9 K+ y2 [; s" D  Yx := seq(a[k], k = 0 .. n)
9 l3 F  ]" v, _) r Basis(pl1, plex(x));
%;
& ]" |5 V, P3 S, ]Error, too many levels of recursion
7 \0 {5 X5 E) Z7 P0 Y: D5 ?Basis(pl1, prod(x));
) Y+ o1 C) _! ?, T. p: @, G% U%;
! M2 G4 a+ I9 E+ nError, too many levels of recursion
  ^& D/ I4 k: m+ _& }: E# P, j 然后显示错误求高手指点，我做的东西最好用a1,a2,...,an这样设置未知数我好编程