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A328608
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Numbers whose binary indices have no part circularly followed by a divisor or a multiple.
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4
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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
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OFFSET
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1,1
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COMMENTS
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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.
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LINKS
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EXAMPLE
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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}
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MATHEMATICA
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Select[Range[100], !MatchQ[Append[Join@@Position[Reverse[IntegerDigits[#, 2]], 1], 1+IntegerExponent[#, 2]], {___, x_, y_, ___}/; Divisible[x, y]||Divisible[y, x]]&]
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CROSSREFS
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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.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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