login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A048200 Minimal length pair-exchange / set-rotate sequence to reverse n distinct ordered elements. 3
0, 1, 2, 4, 10, 15, 23, 32, 42, 55, 67, 84 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
"Rotate" is always a left-rotate (moves leftmost element to the right end) and "Exchange" is always a pair-exchange of the two leftmost elements.
LINKS
Danilo Bazzanella, Antonio Di Scala, Simone Dutto, and Nadir Murru, Primality tests, linear recurrent sequences and the Pell equation, arXiv:2002.08062 [math.NT], 2020.
Sean A. Irvine, Java program (github)
Sai Satwik Kuppili and Bhadrachalam Chitturi, Exact upper bound for sorting R_n with LE, University of Texas at Dallas (2019).
Sai Satwik Kuppili and Bhadrachalam Chitturi, An upper bound for sorting R_n with LRE, arXiv:2002.07342 [cs.DS], 2020.
Sai Satwik Kuppili and Bhadrachalam Chitturi, Exact upper bound for sorting R_n with LE, Discrete Mathematics, Algorithms and Applications, 2020.
FORMULA
Conjecture: a(n) = (3*n^2/4)-2*n if n is even and a(n) = (3*n^2-10*n+15)/4 if n is odd. See links for more information. - Sai Satwik Kuppili and Bhadrachalam Chitturi, Jun 09 2020
EXAMPLE
a(4) = 4 since "xrrx" is the shortest sequence reversing "ABCD". Explicitly, (begin) ABCD, (x)-> BACD, (r)-> ACDB, (r) -> CDBA, (x)-> DCBA.
CROSSREFS
Sequence in context: A351927 A333619 A128513 * A058201 A000947 A125245
KEYWORD
nonn,nice,more
AUTHOR
EXTENSIONS
a(11) added by Sai Satwik Kuppili and Srinath T, Bhadrachalam Chitturi, Jan 02 2019
a(12) from Sean A. Irvine, Jun 04 2021
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)