A129594 Involution of nonnegative integers induced by the conjugation of the partition encoded in the run lengths of binary expansion of n.

0, 1, 3, 2, 4, 7, 6, 5, 11, 12, 15, 8, 9, 14, 13, 10, 20, 27, 28, 19, 16, 31, 24, 23, 22, 25, 30, 17, 18, 29, 26, 21, 43, 52, 59, 36, 35, 60, 51, 44, 47, 48, 63, 32, 39, 56, 55, 40, 41, 54, 57, 38, 33, 62, 49, 46, 45, 50, 61, 34, 37, 58, 53, 42, 84, 107, 116, 75, 68, 123

Offset: 0

Author

Antti Karttunen, May 01 2007

Keywords

• nonn
• look

Comments

This sequence is based on the fact that compositions (i.e. ordered partitions) can be mapped 1-to-1 to partitions by taking the partial sums of the list where one is subtracted from each composant except the first. (See table A227189 where the parts for each partition are listed).

The inverse process, from partitions to compositions, occurs by inserting the first (i.e. smallest) element of a partition sorted into ascending order to the front of the list obtained by adding one to the first differences of the elements.

Compositions map bijectively to nonnegative integers by assigning each run of k consecutive 1's (or 0's) in binary expansion of n with summand k in the composition.

The graph of this sequence is quite interesting.

Examples

			a(8) = 11, as 8 is 1000 in binary, mapping to composition 3+1 (we scan the binary expansion from the least to the most significant end), which maps to partition 3+3, whose conjugate-partition is 2+2+2, yielding composition 2+1+1, which maps to binary 1011, 11 in decimal. a(13) = 14, as 13 is 1101 in binary, mapping to composition 1+1+2, which maps to the partition 1+1+2, whose conjugate-partition is 1+3, yielding composition 1+3, which maps to binary 1110, 14 in decimal. a(11) = 8 and a(14) = 13, as taking the conjugate of a partition is a self-inverse operation.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 0..1023
• Antti Karttunen, Python-program for computing this and related sequences.
• A. Karttunen et al., Run-length encoding, OEIS Wiki.
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

a(n) = A075158(A122111(1+A075157(n)) - 1). See A129595 for another kind of encoding of integer partitions.

Sequences related to partitions encoded in this way:

Cf. A227189 (parts of partitions listed on separate rows of the array).

Cf. A005811 (number of parts in the partition).

Cf. A136480 (for n>= 1, the smallest part).

Cf. A227185 (the largest part).

Cf. A227183 (sum of parts).

Cf. A227184 (product of parts).

Note that this permutation maps between A005811 and A227185 as follows: A005811(n) = A227185(a(n)) and vice versa: A227185(n) = A005811(a(n)). On the other hand, it keeps A227183 fixed, as A227183(n) = A227183(a(n)).

Cf. also A226062.