cp's OEIS Frontend

A355560 Number of configurations of the 8 X 2 variant of the sliding block 15-puzzle that require a minimum of n moves to be reached, starting with the empty square in one of the corners.

%I A355560 #16 Sep 04 2022 12:24:48
%S A355560 1,2,3,6,11,20,37,68,125,227,394,672,1151,1983,3373,5703,9508,15640,
%T A355560 25293,40732,65032,103390,162830,255543,397013,613104,938477,1431068,
%U A355560 2162964,3255845,4860428,7223861,10649867,15628073,22747718,32963838,47397514,67825949,96317070
%N A355560 Number of configurations of the 8 X 2 variant of the sliding block 15-puzzle that require a minimum of n moves to be reached, starting with the empty square in one of the corners.
%C A355560 This sequence was computed by Richard Korf in "Linear-time Disk-Based Implicit Graph Search" (see links), but was not included in the paper.
%H A355560 Ben Whitmore, <a href="/A355560/b355560.txt">Table of n, a(n) for n = 0..140</a>
%H A355560 Richard Korf, <a href="https://www.cs.helsinki.fi/u/bmmalone/heuristic-search-fall-2013/Korf2008.pdf">Linear-time Disk-Based Implicit Graph Search</a>, Journal of the ACM 55 (2008), No. 6.
%e A355560 Starting from the solved configuration
%e A355560    1  2  3  4  5  6  7  8
%e A355560    9 10 11 12 13 14 15
%e A355560 the unique configuration requiring 140 moves is
%e A355560       8  6  5  4  3 10  1
%e A355560   15  7 14 13 12 11  2  9
%o A355560 (Python) # alst(), moves(), swap() in A089473
%o A355560 print(alst("-123456789abcdef", (8, 2), v=True)) # _Michael S. Branicky_, Jul 06 2022
%Y A355560 Cf. A090033, A090034, A090035, A090036, A090167, A346736.
%K A355560 nonn,fini,full
%O A355560 0,2
%A A355560 _Ben Whitmore_, Jul 06 2022