OFFSET

0,2

COMMENTS

This sequence was originally computed by Richard Korf, but the full sequence was not included in his paper. It was later re-computed by Tomas Rokicki.

LINKS

Ben Whitmore, Table of n, a(n) for n = 0..84

Richard Korf, Linear-time Disk-Based Implicit Graph Search, Journal of the ACM 55 (2008), No. 6.

Tomas Rokicki, Twenty-Four puzzle, some observations, 2011.

EXAMPLE

Starting from the solved configuration

1 2 3 4 5

6 7 8 9 10

11 12 13 14

the unique configuration requiring 84 moves is

5 4 3 2 1

10 9 8 7 6

14 13 12 11

PROG

(Python) # alst(), moves(), swap() in A089473

print(alst("-123456789abcde", (5, 3), v=True)) # Michael S. Branicky, Jul 31 2021

CROSSREFS

KEYWORD

nonn,fini,full

AUTHOR

Ben Whitmore, Jul 31 2021

STATUS

approved