OFFSET
0,5
COMMENTS
EXAMPLE
The binary indices of binary indices of 20 are {{1,2},{1,3}}, with choices (1,1), (1,3), (2,1), (2,3), so a(20) = 4.
The binary indices of binary indices of 52 are {{1,2},{1,3},{2,3}}, with choices (1,1,1), (1,1,3), (1,3,2), (1,3,3), (2,1,2), (2,1,3), (2,3,2), (2,3,3), so a(52) = 8.
MATHEMATICA
bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n, 2]], 1];
Table[Length[Tuples[bpe/@bpe[n]]], {n, 0, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 12 2023
STATUS
approved