A086348 On a 3 X 3 board, number of n-move routes of chess king ending in the central square.

1, 8, 32, 168, 784, 3840, 18432, 89216, 430336, 2078720, 10035200, 48457728, 233967616, 1129709568, 5454692352, 26337640448, 127169265664, 614027755520, 2964787822592, 14315262836736, 69120201588736, 333741859799040, 1611448241356800, 7780760413011968, 37568834600697856

Offset

0,2

Comments

From Johannes W. Meijer, Aug 01 2010: (Start)

The a(n) represent the number of n-move paths of a chess king on a 3 X 3 board that end or start in the central square m (m = 5).

Inverse binomial transform of A090390 (without the first leading 1).

(End)

From R. J. Mathar, Oct 12 2010: (Start)

The row n=3 of an array T(n,k) counting king walks on an n X n board starting on a square on the diagonal next to a corner:

1,8,32,168,784,3840,18432,89216,430336,2078720,10035200,48457728,233967616,

1,8,47,275,1610,9425,55175,323000,1890875,11069375,64801250,379353125,

1,8,47,318,2013,13140,84555,547722,3537081,22874400,147831399,955690326,

1,8,47,318,2134,14539,99267,679189,4650100,31848677,218164072,1494530576,

1,8,47,318,2134,14880,103920,733712,5187856,36796224,261164848,1855327584,

1,8,47,318,2134,14880,104885,748845,5382180,38880243,281743740,2045995632,

1,8,47,318,2134,14880,104885,751590,5430735,39556080,289541500,2127935700,

1,8,47,318,2134,14880,104885,751590,5438580,39710495,291852880,2156410817,

1,8,47,318,2134,14880,104885,751590,5438580,39733008,292340803,2164218694,

1,8,47,318,2134,14880,104885,751590,5438580,39733008,292405638,2165752797, (End)

Links

Andrew Howroyd, Table of n, a(n) for n = 0..1000

Mike Oakes, KingMovesForPrimes.

Zak Seidov, KingMovesForPrimes.

Zak Seidov et al., New puzzle? King moves for primes, digest of 28 messages in primenumbers group, Jul 13 - Jul 23, 2003. [Cached copy]

Sleephound, KingMovesForPrimes.

Index entries for linear recurrences with constant coefficients, signature (2,12,8).

Formula

a(n) = (1/16)(4(-2)^(n+1) + (2+sqrt(8))^(n+2) + (2-sqrt(8))^(n+2)).

From Johannes W. Meijer, Aug 01 2010: (Start)

G.f.: ( 1+6*x+4*x^2 ) / ( (2*x+1)*(-4*x^2-4*x+1) ).

a(n) = 2*a(n-1) + 12*a(n-2) + 8*a(n-3) with a(0)=1, a(1)=8 and a(2)=32.

Lim_{k->oo} a(n+k)/a(k) = A084128(n) + 2*A057087(n-1)*sqrt(2). (End)

2*a(n) = 3*A057087(n) + 2*A057087(n-1) - (-2)^n. - R. J. Mathar, May 21 2019

Maple

with(LinearAlgebra): nmax:=19; m:=5; A[5]:= [1, 1, 1, 1, 0, 1, 1, 1, 1]: A:=Matrix([[0, 1, 0, 1, 1, 0, 0, 0, 0], [1, 0, 1, 1, 1, 1, 0, 0, 0], [0, 1, 0, 0, 1, 1, 0, 0, 0], [1, 1, 0, 0, 1, 0, 1, 1, 0], A[5], [0, 1, 1, 0, 1, 0, 0, 1, 1], [0, 0, 0, 1, 1, 0, 0, 1, 0], [0, 0, 0, 1, 1, 1, 1, 0, 1], [0, 0, 0, 0, 1, 1, 0, 1, 0]]): for n from 0 to nmax do B(n):=A^n: a(n):= add(B(n)[m, k], k=1..9): od: seq(a(n), n=0..nmax); # Johannes W. Meijer, Aug 01 2010

Mathematica

Table[(1/16)(4(-2)^(n+1)+(2+Sqrt[8])^(n+2)+(2-Sqrt[8])^(n+2)), {n, 0, 19}]

Crossrefs

Cf. A086346, A086347.

Cf. A179597.

Sequence in context: A188121 A045684 A045675 * A129798 A129792 A224664

Adjacent sequences: A086345 A086346 A086347 * A086349 A086350 A086351

Keyword

nonn,easy

Author

Zak Seidov, Jul 17 2003

Extensions

Offset changed and edited by Johannes W. Meijer, Jul 15 2010

a(21) onward from Andrew Howroyd, Nov 07 2025

Status

approved