Starting with polynomial:
P : t^2 - 1
Extension levels are: 2 21
-------------------------------------------------
Trying to find an order 21 Kronrod extension for:
P1 : t^2 - 1
Solvable: 1
-------------------------------------------------
Ending with final polynomial:
P : t^23 - 27477332587/118894837*t^21 + 2611798498365/118894837*t^19 - 7015431225285/6257623*t^17 + 210645876486150/6257623*t^15 - 3838108917564810/6257623*t^13 + 42284507575966110/6257623*t^11 - 272435422471061850/6257623*t^9 + 956859427232183475/6257623*t^7 - 1604772057804040125/6257623*t^5 + 976872118732985475/6257623*t^3 - 95174230816890225/6257623*t
-------------------------------------------------
Computing nodes and weights
  current precision for roots: 53
  current precision for roots: 106
 current precision for weights: 53
Linear system for weights solvable: 0
  current precision for roots: 106
  current precision for roots: 212
 current precision for weights: 106
Linear system for weights solvable: 1
  current precision for roots: 212
  current precision for roots: 424
 current precision for weights: 212
Linear system for weights solvable: 1
Sufficient bits for target precision reached
-------------------------------------------------
The nodes are:
| (1.2247834340295717544e-372 + 8.2202446111418697264e-373j)  +/-  (3.39e-371, 3.39e-371j)
| (-6.0738715441923626763 - 1.6215747074354509398e-367j)  +/-  (3.96e-122, 3.96e-122j)
| (-6.9866729438547648343 - 2.6389296113905080259e-369j)  +/-  (2.05e-122, 2.05e-122j)
| (6.9866729438547648343 + 1.8260294237165051277e-367j)  +/-  (2.07e-122, 2.07e-122j)
| (8.0746291959306939849 + 1.7992101658924975907e-371j)  +/-  (4.13e-123, 4.13e-123j)
| (-4.4774425907482651199 + 2.5718891733098121291e-375j)  +/-  (3.13e-122, 3.13e-122j)
| (6.0738715441923626763 - 1.6351766702635370879e-374j)  +/-  (3.98e-122, 3.98e-122j)
| (3.7427890670812406218 + 5.3257156621769589714e-385j)  +/-  (1.46e-122, 1.46e-122j)
| (4.4774425907482651199 + 0j)  +/-  (3.43e-122, 3.43e-122j)
| (2.3438242604265436264 + 1.7815335711443451292e-405j)  +/-  (8.59e-124, 8.59e-124j)
| (1.6670270843071127769 - 7.8971493952394981582e-411j)  +/-  (1.32e-124, 1.32e-124j)
| (-3.7427890670812406218 - 8.6926853294036736484e-411j)  +/-  (1.46e-122, 1.46e-122j)
| (0.34517598918116081199 - 2.8896539148255707471e-415j)  +/-  (1.22e-126, 1.22e-126j)
| (-3.0339989333091864518 + 1.8311878972376600459e-412j)  +/-  (4.65e-123, 4.65e-123j)
| (-1.6670270843071127769 + 1.0640055078283191468e-417j)  +/-  (1.28e-124, 1.28e-124j)
| (3.0339989333091864518 - 5.0576911353002841363e-422j)  +/-  (4.52e-123, 4.52e-123j)
| (-5.2486462706828758397 + 6.2034249970291838231e-428j)  +/-  (4.91e-122, 4.91e-122j)
| (5.2486462706828758397 + 7.3327500187431663264e-430j)  +/-  (4.86e-122, 4.86e-122j)
| (-0.34517598918116081199 + 3.1222355836725814941e-437j)  +/-  (1.22e-126, 1.22e-126j)
| (-8.0746291959306939849 - 3.2372943536154714852e-434j)  +/-  (3.93e-123, 3.93e-123j)
| (1 + 2.4426164325277866468e-436j)  +/-  (1.72e-125, 1.72e-125j)
| (-1 + 4.1629807782301086588e-437j)  +/-  (1.51e-125, 1.51e-125j)
| (-2.3438242604265436264 - 2.0463809126721497986e-435j)  +/-  (8.81e-124, 8.81e-124j)
-------------------------------------------------
The weights are:
| (0.025943565103384409637 + 1.9364833195126179426e-371j)  +/-  (2.02e-40, 1.15e-101j)
| (3.3498266805198939486e-09 - 1.7355508410961279674e-375j)  +/-  (7.38e-45, 4.18e-106j)
| (9.7929090497818569344e-12 - 2.8195019098919880685e-377j)  +/-  (3.16e-46, 1.79e-107j)
| (9.7929090497818569344e-12 - 4.5489797342691562743e-378j)  +/-  (1.09e-47, 6.18e-109j)
| (3.4624099190679959733e-15 - 5.6085043816974573288e-380j)  +/-  (3.15e-49, 1.78e-110j)
| (1.327836324819410899e-05 - 2.8754986168719007464e-374j)  +/-  (1.66e-44, 9.41e-106j)
| (3.3498266805198939486e-09 - 3.0121052021943120745e-378j)  +/-  (7.44e-47, 4.22e-108j)
| (0.00026092744457752914835 + 1.9735932491477649572e-374j)  +/-  (2.8e-44, 1.59e-105j)
| (1.327836324819410899e-05 - 3.0995257723994779208e-375j)  +/-  (2.33e-45, 1.32e-106j)
| (0.017468927143921027119 + 3.3313758326434914984e-373j)  +/-  (3.85e-42, 2.18e-103j)
| (0.06675606866209279946 - 1.0240022583732176427e-372j)  +/-  (1.19e-40, 6.73e-102j)
| (0.00026092744457752914835 + 1.0383445766952201697e-373j)  +/-  (4.08e-46, 2.31e-107j)
| (0.23938354697111102226 - 1.1508981902853441254e-371j)  +/-  (7.87e-41, 4.46e-102j)
| (0.0027937393323819865028 - 3.1936894945399556914e-373j)  +/-  (2.25e-45, 1.28e-106j)
| (0.06675606866209279946 - 1.9290723464111700763e-372j)  +/-  (3.06e-43, 1.74e-104j)
| (0.0027937393323819865028 - 9.13764693280098893e-374j)  +/-  (8.61e-45, 4.89e-106j)
| (3.3032510289251758597e-07 + 7.5244824230163904072e-375j)  +/-  (1.65e-48, 9.39e-110j)
| (3.3032510289251758597e-07 + 2.9945347546165384288e-376j)  +/-  (3.82e-48, 2.16e-109j)
| (0.23938354697111102226 - 1.2992408597938143705e-371j)  +/-  (3.09e-43, 1.83e-104j)
| (3.4624099190679959733e-15 + 2.0918846151317635358e-379j)  +/-  (5.69e-53, 3.25e-114j)
| (0.16035139584624929208 + 2.9532057620971697946e-372j)  +/-  (3.78e-44, 2.34e-105j)
| (0.16035139584624929208 + 4.2798745067929614623e-372j)  +/-  (1.07e-44, 7.03e-106j)
| (0.017468927143921027119 + 8.3639081680067289217e-373j)  +/-  (8.7e-46, 4.67e-107j)
