A351205 Numbers whose binary expansion does not have all distinct runs.
5, 9, 10, 17, 18, 20, 21, 22, 26, 27, 33, 34, 36, 37, 40, 41, 42, 43, 45, 46, 51, 53, 54, 58, 65, 66, 68, 69, 72, 73, 74, 75, 76, 77, 80, 81, 82, 83, 84, 85, 86, 87, 89, 90, 91, 93, 94, 99, 100, 101, 102, 105, 106, 107, 108, 109, 110, 117, 118, 119, 122, 129
Offset: 1
Examples
The terms together with their binary expansions begin: 5: 101 41: 101001 74: 1001010 9: 1001 42: 101010 75: 1001011 10: 1010 43: 101011 76: 1001100 17: 10001 45: 101101 77: 1001101 18: 10010 46: 101110 80: 1010000 20: 10100 51: 110011 81: 1010001 21: 10101 53: 110101 82: 1010010 22: 10110 54: 110110 83: 1010011 26: 11010 58: 111010 84: 1010100 27: 11011 65: 1000001 85: 1010101 33: 100001 66: 1000010 86: 1010110 34: 100010 68: 1000100 87: 1010111 36: 100100 69: 1000101 89: 1011001 37: 100101 72: 1001000 90: 1011010 40: 101000 73: 1001001 91: 1011011 For example, 77 has binary expansion 1001101, with runs 1, 00, 11, 0, 1, which are not all distinct, so 77 is in the sequence.
Links
- Mathematics Stack Exchange, What is a sequence run? (answered 2011-12-01)
Crossrefs
A000120 counts binary weight.
A011782 counts integer compositions.
A242882 counts compositions with distinct multiplicities.
A318928 gives runs-resistance of binary expansion.
A325545 counts compositions with distinct differences.
A334028 counts distinct parts in standard compositions.
A351014 counts distinct runs in standard compositions.
Counting words with all distinct runs:
- A351202 = permutations of prime factors.
Programs
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Maple
q:= proc(n) uses ListTools; (l-> is(nops(l)<>add( nops(i), i={Split(`=`, l, 1)}) +add( nops(i), i={Split(`=`, l, 0)})))(Bits[Split](n)) end: select(q, [$1..200])[]; # Alois P. Heinz, Mar 14 2022
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Mathematica
Select[Range[0,100],!UnsameQ@@Split[IntegerDigits[#,2]]&]
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Python
from itertools import groupby, product def ok(n): runs = [(k, len(list(g))) for k, g in groupby(bin(n)[2:])] return len(runs) > len(set(runs)) print([k for k in range(130) if ok(k)]) # Michael S. Branicky, Feb 09 2022
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