OFFSET
1,1
LINKS
S. E. Thornton, Properties of the Bohemian family of n x n matrices with population {0, 1, 2}, Characteristic Polynomial Database.
PROG
(Python)
from itertools import product
from sympy.matrices import Matrix
def a(n):
eigset = set()
for e in product([0, 1, 2], repeat=n*n):
if n > 1 and e[1] > e[n]: continue
M = Matrix([list(e[n*r:n*(r+1)]) for r in range(n)])
eigset |= set(eig for eig in M.eigenvals().keys())
return len(eigset)
print([a(n) for n in range(1, 3)]) # Michael S. Branicky, Mar 25 2021
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Steven E. Thornton, Mar 10 2019
STATUS
approved