OFFSET
0,2
COMMENTS
The 15-block puzzle is often referred to (incorrectly) as Sam Loyd's 15-Puzzle.
Sum of sequence terms = A088020(5)/2.
152 <= (number of last sequence term) <= 205 (see A087725 and cube archives link for current status). - Hugo Pfoertner, Feb 12 2020
REFERENCES
See A087725 for references.
LINKS
Robert Clausecker, term generator puzzledist.c
Robert Clausecker, The Quality of Heuristic Functions for IDA*, Zuse Institute Berlin (2020).
Hugo Pfoertner, Configuration counts for n*n sliding block puzzles.
Tomas Rokicki, comment in Twenty-Four puzzle, some observations
Ben Whitmore in the Cube Forum, 5x5 sliding puzzle can be solved in 205 moves, with updates by Johan de Ruiter claiming 182 moves.
PROG
(Fortran) See link in A089473.
(C) See Clausecker link.
(Python) # alst(), moves(), swap() in A089473
start, shape = "-123456789ABCDEFGHIJKLMNO", (5, 5)
alst(start, shape, v=True) # Michael S. Branicky, Dec 31 2020
CROSSREFS
KEYWORD
fini,hard,nonn
AUTHOR
Hugo Pfoertner, Nov 25 2003
EXTENSIONS
More terms from Tomas Rokicki, Aug 09 2011
a(28)-a(30) from Robert Clausecker, Jan 29 2018
a(31)-a(32) from Robert Clausecker, Sep 14 2020
STATUS
approved