OFFSET
1,1
COMMENTS
All terms are multiples of 5 by symmetry. Michael S. Branicky, May 20 2021
EXAMPLE
Some solutions for n = 6:
..4....2....0....2....3....3....4....4....4....2....0....1....1....0....1....4
..2....1....4....4....1....2....0....3....0....4....2....0....3....3....0....3
..4....2....1....2....3....0....1....2....2....2....3....3....1....1....3....4
..0....4....2....3....4....1....4....1....3....3....0....2....2....2....4....2
..1....0....4....4....0....2....2....3....4....1....4....1....0....4....0....4
..0....1....1....2....1....1....0....4....3....3....3....0....3....1....4....1
PROG
(Python)
from itertools import product
def a(n):
if n == 1: return 5
squares = ["".join(u) + "".join(u)
for r in range(1, n//2 + 1) for u in product("01234", repeat = r)]
words = ("0"+"".join(w) for w in product("01234", repeat=n-1))
return 5*sum(all(s not in w for s in squares) for w in words)
print([a(n) for n in range(1, 10)]) # Michael S. Branicky, May 20 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Jul 30 2012
STATUS
approved