login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A125106 Enumeration of partitions by binary representation: each 1 is a part; the part size is 1 more than the number of zeros in the rest of the number. 17
1, 2, 1, 1, 3, 2, 1, 2, 2, 1, 1, 1, 4, 3, 1, 3, 2, 2, 1, 1, 3, 3, 2, 2, 1, 2, 2, 2, 1, 1, 1, 1, 5, 4, 1, 4, 2, 3, 1, 1, 4, 3, 3, 2, 1, 3, 2, 2, 2, 1, 1, 1, 4, 4, 3, 3, 1, 3, 3, 2, 2, 2, 1, 1, 3, 3, 3, 2, 2, 2, 1, 2, 2, 2, 2, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Another way to describe this: starting with the binary representation and a counter set at one, count the zeros from right to left. Write a term equal to the counter for each "1" encountered.

A101211 is a similar sequence with A005811 elements per row which maps natural numbers to compositions (ordered partitions).

There are two ways to consider this as a table: taking each partition as a row, or taking the partitions generated by 2^(n-1) through 2^n-1 as a row.

Taking the n-th row as multiple partitions, it consists of those partitions with the first hook size (largest part plus number of parts minus 1) equal to n. The number of integers in this n-th row is A001792(n-1), and the row sum is A049611.

Taking each partition as a separate row, the row lengths are A000120, and the row sums are A161511.

LINKS

Alois P. Heinz, Rows n = 1..12, flattened

FORMULA

Partition 2n is partition n with every part size increased by 1; partition 2n+1 is partition n with an additional part of size 1.

EXAMPLE

Row 4:

1000 [4]

1001 [3,1]

1010 [3,2]

1011 [2,1,1]

1100 [3,3]

1101 [2,2,1]

1110 [2,2,2]

1111 [1,1,1,1]

MAPLE

b:= proc(n) local c, l, m; l:=[][]; m:= n; c:=1;

      while m>0 do if irem(m, 2, 'm')=0 then c:= c+1

         else l:= c, l fi

      od; l

    end:

T:= n-> seq(b(i), i=2^(n-1)..2^n-1):

seq(T(n), n=1..7);  # Alois P. Heinz, Sep 25 2015

MATHEMATICA

f[k_] := (bits = IntegerDigits[k, 2]; zerosCount = Reverse[ Accumulate[ 1-Reverse[bits] ] ] + 1; Select[ Transpose[ {bits, zerosCount} ], First[#] == 1 & ][[All, 2]]); row[n_] := Table[ f[k], {k, 2^(n-1), 2^n-1}]; Flatten[ Table[ row[n], {n, 1, 5}]] (* Jean-Fran├žois Alcover, Jan 24 2012 *)

CROSSREFS

Cf. A000041, A000120, A161511, A005811, A037016, A101211, A001792, A049611, A126411.

Cf. A005940. - Franklin T. Adams-Watters, Mar 06 2010

Sequence in context: A272121 A273135 A165162 * A229874 A243611 A273102

Adjacent sequences:  A125103 A125104 A125105 * A125107 A125108 A125109

KEYWORD

tabf,nice,nonn

AUTHOR

Alford Arnold, Dec 10 2006

EXTENSIONS

Edited by Franklin T. Adams-Watters, Jun 11 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified March 28 22:27 EDT 2017. Contains 284249 sequences.