The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A330280 Least number of 2 X 2 rotations required to solve an n X n Simon Tatham's Twiddle puzzle. 1
 0, 2, 10, 24 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The puzzle is as follows. An n X n grid is filled with distinct integers from 1 to n*n, such that the number at row r and column c (both 0-based) is n*n - (r*n + c). The task is to perform rotations of 2 X 2 sub-grids (moves) to bring the numbers into their natural order, i.e., the number at row r and column c should become r*n + c + 1. Rotations are by 90 degrees in the clockwise or counterclockwise direction. See links for example puzzles and solutions. Wladimir Leite found strong upper bounds for the next few terms: 48, 88 and 146 (see links). - Dmitry Kamenetsky, Apr 20 2020 LINKS greenturtle3141, What is the strategy to solve Simon Tatham's Twiddle?, Puzzling StackExchange, Dec 24 2016. greenturtle3141, A Guide to the Number Rotation Puzzle, Puzzling StackExchange, May 27 2019. Dmitry Kamenetsky, Rotating numbers in a 3x3 grid, Puzzling StackExchange, Feb 15 2020. Dmitry Kamenetsky and Wladimir Leite, Best known solutions for 3 <= n <= 7 Simon Tatham, Twiddle 3x3 puzzle Topcoder, Marathon Match 117 - RotatingNumbers CROSSREFS Sequence in context: A293403 A316451 A120845 * A293412 A224837 A049450 Adjacent sequences:  A330277 A330278 A330279 * A330281 A330282 A330283 KEYWORD nonn,hard,more AUTHOR Dmitry Kamenetsky, Feb 29 2020 EXTENSIONS Removed a(5) as it was found to be sub-optimal - Dmitry Kamenetsky, Apr 16 2020 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 30 15:55 EDT 2020. Contains 337439 sequences. (Running on oeis4.)