identity det(zI-A-BKC) * kappa = det[V(z); [K|I] g^{-1}] verified on 6 random K: True  kappa = -15
n = 8  common denominator of (A,B,C): 15
written ../out/cert_24_nice_int.ABC.json
A =
   ['-5/3', '13/15', '1', '0', '0', '0', '0', '0']
   ['-1/3', '-1/15', '0', '1', '0', '0', '0', '0']
   ['2/3', '1/3', '0', '0', '1', '0', '0', '0']
   ['0', '-3/5', '0', '0', '0', '1', '0', '0']
   ['-1', '-3/5', '0', '0', '0', '0', '1', '0']
   ['5/3', '-2/3', '0', '0', '0', '0', '0', '1']
   ['-4/3', '23/15', '0', '0', '0', '0', '0', '0']
   ['-2/3', '-2/15', '0', '0', '0', '0', '0', '0']
B =
   ['27/5', '-251/15', '12/5', '-12/5']
   ['16/5', '32/15', '-4/5', '-26/5']
   ['0', '4/3', '0', '-3']
   ['-11/5', '1/5', '-1/5', '-24/5']
   ['-31/5', '-24/5', '4/5', '11/5']
   ['-2', '34/3', '-8', '-6']
   ['27/5', '-151/15', '47/5', '-12/5']
   ['-23/5', '-11/15', '7/5', '8/5']
C =
   ['1', '0', '0', '0', '0', '0', '0', '0']
   ['0', '1', '0', '0', '0', '0', '0', '0']
