t = sum_(i=1..6) g_i(t)^7,  g_i(t) = c_i0 + c_i1 t + ... (centre values to 22 digits; '*' = exact fixed value)
g_1:  c_10 = (0.82) + (0) i *;   c_11 = (0.2802423785856134212888) + (-0.5662133153306539879481) i  ;   c_12 = (0.2930500553194012474714) + (-0.5380730324996646190777) i  
g_2:  c_20 = (-0.1233548866424642678865) + (-0.09204896224424802479626) i  ;   c_21 = (0.26) + (-0.14) i *;   c_22 = (-0.3441549107636504465062) + (-0.6683042447524640188283) i  
g_3:  c_30 = (-0.362948105458665203846) + (0.2964459582461123048292) i  ;   c_31 = (-0.81) + (0.83) i *;   c_32 = (0.4598767682968168069586) + (0.3857140150963832788452) i  
g_4:  c_40 = (-0.2881831474025180760676) + (-0.2032496420153313223914) i  ;   c_41 = (-0.526651080237465293044) + (0.4225580597876092092891) i  ;   c_42 = (0.3171838841804207733374) + (0.7499942739750682661801) i  
g_5:  c_50 = (-0.78861523275524249583) + (0.1174979033558355317566) i  ;   c_51 = (-0.5843239594732303725002) + (0.3739358653618323611329) i  ;   c_52 = (-0.1238368183920909594116) + (0.7029882662695372925004) i  
g_6:  c_60 = (0.08060769552048333485625) + (0.8038504969292300380366) i  ;   c_61 = (-0.2199166636625268390803) + (-0.1820713874698624636086) i  ;   c_62 = (-0.1005012179507068919251) + (0.0395193216360292243571) i  
homogeneous form: x*y^13 = sum_i G_i(x,y)^7,  G_i = sum_j c_ij x^j y^(2-j)
coefficients of sum g_i^k - t at the centre (exact, shown as floats):
  4.9e-61, 2.6e-60, 1.3e-59, 2.4e-59, 5.0e-59, 7.8e-59, 1.0e-58, 1.4e-58, 1.6e-58, 1.1e-58, 1.0e-58, 5.7e-59, 1.9e-59, 4.1e-60, 8.0e-61
