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A112509 Maximum number of numbers represented by substrings of an n-bit number's binary representation. 6
1, 3, 5, 7, 10, 13, 17, 22, 27, 33, 40, 47, 55, 64, 73, 83, 94, 106, 118, 131, 145, 160, 176, 192, 209, 227, 246, 265, 285, 306, 328 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Substrings must be contiguous, they are treated as stand-alone binary representations and the reversal of substrings is not permitted.

LINKS

Table of n, a(n) for n=1..31.

2008/9 British Mathematical Olympiad Round 2: Jan 29 2009, Problem 4 [From Joseph Myers, Feb 01 2009]

EXAMPLE

To see why a(4)=7 (and A112510(4)=12 and A112511(4)=14), consider all numbers whose binary representations require exactly 4 bits: 1000, 1001, 1010, 1011, 1100, 1101, 1110 and 1111. For each of these binary representations in turn, we find the nonnegative integers represented by all of its contiguous substrings. We count these distinct integer values (putting the count in {}s):

1000: any 0, either 00, or 000 -> 0, 1 -> 1, 10 -> 2, 100 -> 4, 1000 -> 8 {5};

1001: either 0, or 00 -> 0, either 1, 01, or 001 -> 1, 10 -> 2, 100 -> 4, 1001 -> 9 {5};

(For brevity, binary substrings are shown below only if they produce values not shown yet.)

1010: 0, 1, 2, 101 -> 5, 1010 -> 10 {5};

1011: 0, 1, 2, 11 -> 3, 5, 1011 -> 11 {6};

1100: 0, 1, 2, 3, 4, 110 -> 6, 1100 -> 12 {7};

1101: 0, 1, 2, 3, 5, 6, 1101 -> 13 {7};

1110: 0, 1, 2, 3, 6, 111 -> 7, 1110 -> 14 {7};

1111: 1, 3, 7, 1111 -> 15 {4}.

Because the maximum number of distinct integer values {in brackets} is 7, a(4)=7. The smallest 4-bit number for which 7 distinct values are found is 12, so A112510(4)=12. The largest 4-bit number for which 7 are found is 14, so A112511(4)=14. (For n=4 the count is a(n)=7 also for all values (only one, 13, here) between A112510(n) and A112511(n). This is not the case in general.).

CROSSREFS

Cf. A112510 (least n-bit number for which this maximum occurs), A112511 (greatest n-bit number for which this maximum occurs).

A078822, A122953, A156022, A156023, A156024, A156025. Equals A156022(n)+1 for n >= 2. [From Joseph Myers, Feb 01 2009]

Sequence in context: A195311 A184013 A057672 * A296846 A173137 A310020

Adjacent sequences:  A112506 A112507 A112508 * A112510 A112511 A112512

KEYWORD

base,nonn

AUTHOR

Rick L. Shepherd, Sep 09 2005

EXTENSIONS

a(21) to a(31) from Joseph Myers, Feb 01 2009

STATUS

approved

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Last modified May 25 23:28 EDT 2020. Contains 334607 sequences. (Running on oeis4.)