A328608 Numbers whose binary indices have no part circularly followed by a divisor or a multiple.

6, 12, 18, 20, 22, 24, 28, 30, 40, 48, 56, 66, 68, 70, 72, 76, 78, 80, 82, 84, 86, 88, 92, 94, 96, 104, 108, 110, 112, 114, 116, 118, 120, 124, 126, 132, 144, 148, 156, 160, 172, 176, 180, 188, 192, 196, 204, 208, 212, 220, 224, 236, 240, 244, 252, 258, 264

Offset: 1

Author

Gus Wiseman, Oct 25 2019

Keywords

• nonn

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.

Circularity means the last part is followed by the first.

Note that this is a somewhat degenerate case, as a part could only be followed by a divisor if it is the last part followed by the first.

Examples

			The sequence of terms together with their binary expansions and binary indices begins:
    6:       110 ~ {2,3}
   12:      1100 ~ {3,4}
   18:     10010 ~ {2,5}
   20:     10100 ~ {3,5}
   22:     10110 ~ {2,3,5}
   24:     11000 ~ {4,5}
   28:     11100 ~ {3,4,5}
   30:     11110 ~ {2,3,4,5}
   40:    101000 ~ {4,6}
   48:    110000 ~ {5,6}
   56:    111000 ~ {4,5,6}
   66:   1000010 ~ {2,7}
   68:   1000100 ~ {3,7}
   70:   1000110 ~ {2,3,7}
   72:   1001000 ~ {4,7}
   76:   1001100 ~ {3,4,7}
   78:   1001110 ~ {2,3,4,7}
   80:   1010000 ~ {5,7}
   82:   1010010 ~ {2,5,7}
   84:   1010100 ~ {3,5,7}
		

Crossrefs

The composition version is A328599.

The necklace composition version is A328601.

Compositions with no consecutive divisors or multiples are A328508.

Numbers whose binary indices are pairwise indivisible are A326704.

Cf. A000031, A318726, A318729, A328171, A328460, A328593, A328598, A328600, A328603.

Programs

Mathematica

Select[Range[100],!MatchQ[Append[Join@@Position[Reverse[IntegerDigits[#,2]],1],1+IntegerExponent[#,2]],{_,x_,y_,_}/;Divisible[x,y]||Divisible[y,x]]&]