OFFSET
1,2
EXAMPLE
For n = 3 the base-2 representations of 1, 2, 3 are the words 1, 10, 11. Of the 6 permutations of these words, the a(3) = 2 permutations 1,10,11 and 11,10,1 are unambiguous when the commas are removed, since 11011 and 11101 each arise from a unique permutation. On the other hand, the permutations 1,11,10 and 11,1,10 are ambiguous when the commas are removed because they become the same word; similarly, 10,1,11 and 10,11,1 become the same word.
MATHEMATICA
Table[Count[Counts[Join @@@ Permutations[(IntegerDigits[#, 2] &) /@ Range[1, n]]], 1], {n, 1, 8}]
PROG
(Python)
from collections import Counter
from itertools import permutations
def A349529(n): return len(list(filter(lambda x: x == 1, Counter(''.join(d) for d in permutations(bin(i)[2:] for i in range(1, n+1))).values()))) # Chai Wah Wu, Nov 22 2021
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Eric Rowland, Nov 20 2021
EXTENSIONS
a(13)-a(15) from Martin Ehrenstein, Nov 23 2021
STATUS
approved