Revision history [back]

You are absolutely right, while being correct on positive integers, the expression is not correct when specialized to k=0:

sage: [B.subs(k=i) == A^i for i in range(20)]
[False,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True,
 True]
sage: B.subs(k=0)
[ -1  -4  -8]
[1/2   2   2]
[  0   0   1]

Thanks for reporting, it is now trac ticket 25520