OFFSET
1,7
COMMENTS
See A210109 for further information.
REFERENCES
Computed by David Scambler, Mar 19 2012
PROG
(Python)
from itertools import product, combinations, permutations
def is4div(b):
for i, j, k in combinations(range(1, len(b)), 3):
divisions = [b[:i], b[i:j], b[j:k], b[k:]]
all_greater = True
for p, bp in enumerate(permutations(divisions)):
if p == 0: continue
if b >= "".join(bp): all_greater = False; break
if all_greater: return True
return False
def a(n): return sum(is4div("".join(b)) for b in product("01", repeat=n))
print([a(n) for n in range(1, 14)]) # Michael S. Branicky, Aug 27 2021
CROSSREFS
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Mar 20 2012
EXTENSIONS
a(18)-a(24) from Michael S. Branicky, Aug 27 2021
STATUS
approved