OFFSET
1,3
COMMENTS
A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793.
EXAMPLE
The terms together with their binary expansions and binary indices begin:
0: 0 ~ {}
1: 1 ~ {1}
2: 10 ~ {2}
3: 11 ~ {1,2}
4: 100 ~ {3}
5: 101 ~ {1,3}
6: 110 ~ {2,3}
7: 111 ~ {1,2,3}
16: 10000 ~ {5}
17: 10001 ~ {1,5}
18: 10010 ~ {2,5}
19: 10011 ~ {1,2,5}
20: 10100 ~ {3,5}
21: 10101 ~ {1,3,5}
22: 10110 ~ {2,3,5}
23: 10111 ~ {1,2,3,5}
32: 100000 ~ {6}
33: 100001 ~ {1,6}
48: 110000 ~ {5,6}
49: 110001 ~ {1,5,6}
64: 1000000 ~ {7}
65: 1000001 ~ {1,7}
66: 1000010 ~ {2,7}
MATHEMATICA
bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n, 2]], 1];
Select[Range[0, 100], SquareFreeQ[Times@@bpe[#]]&]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Gus Wiseman, Mar 25 2024
STATUS
approved