A027683 -id:A027683 - cp's OEIS frontend

A006506 Number of n X n binary matrices with no 2 adjacent 1's, or number of configurations of non-attacking princes on an n X n board, where a "prince" attacks the four adjacent (non-diagonal) squares. Also number of independent vertex sets in an n X n grid.

1, 2, 7, 63, 1234, 55447, 5598861, 1280128950, 660647962955, 770548397261707, 2030049051145980050, 12083401651433651945979, 162481813349792588536582997, 4935961285224791538367780371090, 338752110195939290445247645371206783, 52521741712869136440040654451875316861275

Offset: 0

N. J. A. Sloane, R. H. Hardin, Paul Zimmermann

A two-dimensional generalization of the Fibonacci numbers.
Also the number of vertex covers in the n X n grid graph P_n X P_n.
A181030 (Number of n X n binary matrices with no leading bitstring in any row or column divisible by 4) is the same sequence. Proof from Steve Butler, Jan 26 2015: This is trivially true. A181030 is equivalent to this sequence by interchanging the roles of 0 and 1. In particular, A181030 looks for binary matrices with no leading bitstring divisible by 4, but a bitstring is divisible by 4 if and only if its last two digits is 0; in a binary matrix this can only be avoided if there are no two adjacent 0's (i.e., for any two adjacent 0's take the bitstring starting in that row or column and we are done); the present sequence looks for no two adjacent 1's. Similar reasons show that the array A181031 is equivalent to the array A089980.
Let R(n) be the set of squares that have vertices at integer coordinates and lie in the region of the plane |x|+|y| <= n+1, and let S(n) be the set of squares that have vertices at integer coordinates and lie in the region of the plane |x|+|y-1/2| <= n+2.  Further let T be the collection of rectangular tiles with dimensions i X 1 or 1 X i with i arbitrary.  Then a(2n) is the number of ways to tile R(n) using tiles from T and a(2n+1) is the number of ways to tile S(n) using tiles from T. (Note R(n) is the Aztec diamond of order n.) - Steve Butler, Jan 26 2015

Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 342-349.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Jin-Guo Liu, Table of n, a(n) for n = 0..39 (terms 1..33 from Robert Gerbicz, 34..35 from P. Butera and M. Pernici, 37..38 from Casey Mills Davis)
P. Butera and M. Pernici, Sums of permanental minors using Grassmann algebra, arXiv preprint arXiv:1406.5337 [hep-lat], 2014.
Casey Mills Davis, C++ program used to generate a(n) for n = 36..37
Steven R. Finch, Hard Square Entropy Constant [Broken link]
Steven R. Finch, Hard Square Entropy Constant [From the Wayback machine]
Xuanzhao Gao, Xiaofeng Li, and Jinguo Liu, Programming guide for solving constraint satisfaction problems with tensor networks, arXiv:2501.00227 [physics.comp-ph], 2024. See p. 24.
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p.372.
Jin-Guo Liu, Xun Gao, Madelyn Cain, Mikhail D. Lukin and Sheng-Tao Wang, Computing solution space properties of combinatorial optimization problems via generic tensor networks, arXiv:2205.03718 [cond-mat.stat-mech], 2022. Terms 38..39.
I. Mezo, Periodicity of the Last Digits of Some Combinatorial Sequences, J. Int. Seq. 17 (2014) #14.1.1.
B. D. Stosic, T. Stosic, I. P. Fittipaldi and J. J. P. Veerman, Residual entropy of the square Ising antiferromagnet in the maximum critical field: the Fibonacci matrix, Journal of Physics A: Mathematical and General, Volume 30, Number 10, 1997, pp. L331-L337.
Peter Tittmann, Enumeration in Graphs
Eric Weisstein's World of Mathematics, (0,1)-Matrix
Eric Weisstein's World of Mathematics, Grid Graph
Eric Weisstein's World of Mathematics, Hard Square Entropy Constant
Eric Weisstein's World of Mathematics, Independent Vertex Set
Eric Weisstein's World of Mathematics, Vertex Cover
Index entries for sequences related to binary matrices

Cf. A027683 for toroidal version.
Table of values for n x m matrices: A089934.
Cf. A232833 for refinement by number of 1's.
Cf. also A191779.
Cf. A201511, A212270.

A006506 := proc(N) local i,j,p,q; p := 1+x11;
if n=0 then return 1 fi;
for i from 2 to N do
   q := p-select(has,p,x||(i-1)||1);
   p := p+expand(q*x||i||1)
od;
for j from 2 to N do
   q := p-select(has,p,x1||(j-1));
   p := subs(x1||(j-1)=1,p)+expand(q*x1||j);
   for i from 2 to N do
      q := p-select(has,p,{x||(i-1)||j,x||i||(j-1)});
      p := subs(x||i||(j-1)=1,p)+expand(q*x||i||j);
   od
od;
map(icontent,p)
end:
seq(A006506(n), n=0..15);

a[n_] := a[n] = (p = 1 + x[1, 1]; Do[q = p - Select[p, ! FreeQ[#, x[i-1, 1]] &]; p = p + Expand[q*x[i, 1]], {i, 2, n}]; Do[q = p - Select[p, ! FreeQ[#, x[1, j-1]] &]; p = (p /. x[i, j-1] :> 1) + Expand[q*x[1, j]]; Do[q = p - Select[ p, ! FreeQ[#, x[i-1, j]] || ! FreeQ[#, x[i, j-1]] &]; p = (p /. x[i, j-1] :> 1) + Expand[q*x[i, j]], {i, 2, n}], {j, 2, n}]; p /. x[, ] -> 1); a /@ Range[14] (* Jean-François Alcover, May 25 2011, after Maple prog. *)
Table[With[{g = GridGraph[{n, n}]}, Count[Subsets[Range[n^2], Length @ First @ FindIndependentVertexSet[g]], ?(IndependentVertexSetQ[g, #] &)]], {n, 5}] (* _Eric W. Weisstein, May 28 2017 *)

a(n)=L=fibonacci(n+2);p=v=vector(L,i,1);c=0; for(i=0,2^n-1,j=i;while(j&&j%4<3,j\=2);if(j%4<3,p[c++]=i)); for(i=2,n,w=vector(L,j,0); for(j=1,L, for(k=1,L,if(bitand(p[j],p[k])==0,w[j]+=v[k])));v=w); sum(i=1,L,v[i]) \\ Robert Gerbicz, Jun 17 2011

Limit_{n->oo} a(n)^(1/n^2) = c1 = 1.50304... is the hard square entropy constant A085850. - Benoit Cloitre, Nov 16 2003
a(n) appears to behave like A * c3^n * c1^(n^2) where c1 is as above, c3 = 1.143519129587 approximately, A = 1.0660826 approximately. This is based on numerical analysis of a(n) for n up to 19. - Brendan McKay, Nov 16 2003
From n up to 39 we have A = 1.06608266035... - Vaclav Kotesovec, Jan 29 2024

Sequence extended by Paul Zimmermann, Mar 15 1996
Maple program updated and sequence extended by Robert Israel, Jun 16 2011
a(0)=1 prepended by Alois P. Heinz, Jan 29 2024

A066864 Number of binary arrangements without adjacent 1's on n X n rhombic hexagonal grid.

Original entry on oeis.org

1, 2, 6, 42, 524, 13322, 647252, 61758332, 11435477118, 4129523869606, 2902264461628298, 3973109800760143708, 10590895512774862686570, 54979738656662942307796576, 555797909644630436677137498230, 10941698340065066230952215658836402, 419471520990343359533179780148504998680

Offset: 0

R. H. Hardin, Jan 25 2002

Also the number of tilings of an (n+1) X (n+1) square using 1 X 1 squares and L-tiles. An L-tile is a 2 X 2 square with the upper right 1 X 1 subsquare removed and no rotations are allowed. a(2) = 6:
  .___   ___   ___   ___   ___   ___
  |||_| | ||| |||_| || || |||_| || ||
  |||_| |_|_| | ||| ||__| || || | |_|
  |||_| |||_| |_|_| |||_| ||__| |_|_| - Alois P. Heinz, Jun 06 2013

			Neighbors for n=4:
  o--o--o--o
  | /| /| /|
  |/ |/ |/ |
  o--o--o--o
  | /| /| /|
  |/ |/ |/ |
  o--o--o--o
  | /| /| /|
  |/ |/ |/ |
  o--o--o--o

Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 342-349.
J. Katzenelson and R. P. Kurshan, S/R: A Language for Specifying Protocols and Other Coordinating Processes, pp. 286-292 in Proc. IEEE Conf. Comput. Comm., 1986.

Vaclav Kotesovec and Alois P. Heinz, Table of n, a(n) for n = 0..28
Steven R. Finch, Hard Square Entropy Constant [Broken link]
Steven R. Finch, Hard Square Entropy Constant [From the Wayback machine]
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, pp. 69-71.

Cf. A006506, A027683, A066863, A066865, A066866.

Main diagonal of A219741 and A226444.

a:= proc(n) option remember; local b; b:=
      proc(n, l) option remember; local k;
        if n<2 then 1
      elif min(l[])>0 then b(n-1, map(h->h-1, l))
      else for k while l[k]>0 do od; b(n, subsop(k=1, l))+
           `if`(n>1 and kAlois P. Heinz, Aug 26 2013

$RecursionLimit = 1000; a[n0_] := a[n0] = Module[{b}, b[n_, l_List] := b[n, l] = Module[{k}, Which[n<2, 1, Min[l]>0, b[n-1, l-1], True, For[k = 1, l[[k]] > 0, k++]; b[n, ReplacePart[l, k -> 1]] + If[n>1 && k 2, k+1 -> 1}]], 0]]];  b[n0+1, Array[0&, n0+1]]]; Table[a[n], {n, 0, 15}] (* Jean-François Alcover, Feb 24 2015, after Alois P. Heinz *)

Limit_{n->oo} a(n)^(1/n^2) = 1.395485972... (see A085851).

a(12)-a(21) from Vaclav Kotesovec, May 01 2012
a(0) and a(22) from Alois P. Heinz, Aug 26 2013
a(23) from Alois P. Heinz, Aug 28 2013
a(24) from Vaclav Kotesovec, Sep 19 2014
a(25) from Alois P. Heinz, Dec 03 2014
a(26)-a(28) from Vaclav Kotesovec, Aug 13 2016

A067966 Number of binary arrangements without adjacent 1's on n X n array connected n-s.

Original entry on oeis.org

1, 2, 9, 125, 4096, 371293, 85766121, 52523350144, 83733937890625, 350356403707485209, 3833759992447475122176, 109879109551310452512114617, 8243206936713178643875538610721, 1619152874321527556575810000000000000

Offset: 0

R. H. Hardin, Feb 02 2002

Central coefficients of triangle A210341.

			Neighbors for n=4:
o o o o
| | | |
| | | |
o o o o
| | | |
| | | |
o o o o
| | | |
| | | |
o o o o

Vincenzo Librandi, Table of n, a(n) for n = 0..60
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 69, 380.

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw nw-se A067960, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.

Cf. A100399, A210343, A210341.

[Fibonacci(n+2)^n: n in [0..13]]; // Bruno Berselli, Mar 28 2012

Mathematica
```
Table[Fibonacci[n+2]^n, {n, 0, 100}]
```
Maxima
```
makelist(fib(n+2)^n, n, 0, 14);
```

a(n)=fibonacci(n+2)^n \\ Charles R Greathouse IV, Mar 28 2012

a(n) = F(n+2)^n, where F(n) = A000045(n) is the n-th Fibonacci number.

a(n) ~ phi^2/sqrt(5) phi^n^2. [Charles R Greathouse IV, Mar 28 2012]

Edited by Dean Hickerson, Feb 15 2002

A066866 Number of binary arrangements without adjacent 1's in n X n rhombic hexagonal grid torus.

Original entry on oeis.org

1, 5, 22, 201, 4216, 162314, 12329633, 1831137521, 528106112383, 296848246952000, 324932515409958655, 692572885398506075946, 2874785146216927021053015, 23237716875160177498526082523, 365789982527236500400197753931927, 11212996751916827855636781928754023265

Offset: 1

R. H. Hardin, Jan 25 2002

			neighbors for n=4:
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|

Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 342-349.
J. Katzenelson and R. P. Kurshan, S/R: A Language for Specifying Protocols and Other Coordinating Processes, pp. 286-292 in Proc. IEEE Conf. Comput. Comm., 1986.

Sean A. Irvine, Table of n, a(n) for n = 1..18
Steven R. Finch, Hard Square Entropy Constant [Broken link]
Steven R. Finch, Hard Square Entropy Constant [From the Wayback machine]
Sean A. Irvine, Java program (github)
V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 73.

Cf. A006506, A027683, A066863, A066864, A066865.

Terms a(11)-a(12) from Vaclav Kotesovec, May 07 2012
a(13) from Vaclav Kotesovec, Aug 15 2016
a(14) from Vaclav Kotesovec, May 24 2021
a(15)-a(16) from Sean A. Irvine, Nov 18 2023

A067961 Number of binary arrangements without adjacent 1's on n X n torus connected n-s.

Original entry on oeis.org

1, 9, 64, 2401, 161051, 34012224, 17249876309, 23811286661761, 84590643846578176, 792594609605189126649, 19381341794579313317802199, 1242425797286480951825250390016, 208396491430277954192889648311785961, 91534759488004239323168528670973468727049

Offset: 1

R. H. Hardin, Feb 02 2002

			Neighbors for n=4:
| | | |
o o o o
| | | |
| | | |
o o o o
| | | |
| | | |
o o o o
| | | |
| | | |
o o o o
| | | |

Vincenzo Librandi, Table of n, a(n) for n = 1..69
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 409.

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw nw-se A067960, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, e-w n-s A027683, e-w ne-sw n-s A066866.
Cf. A156216. - Paul D. Hanna, Sep 13 2010
Cf. A215941.

[Lucas(n)^n: n in [1..15]]; // Vincenzo Librandi, Mar 15 2014

a:= n-> (<<0|1>, <1|1>>^n. <<2, 1>>)[1$2]^n:
seq(a(n), n=1..15);  # Alois P. Heinz, Aug 01 2021

Table[LucasL[n]^n,{n,15}] (* Harvey P. Dale, Mar 13 2014 *)

a(n) = L(n)^n, where L(n) = A000032(n) is the n-th Lucas number.
Logarithmic derivative of A156216. - Paul D. Hanna, Sep 13 2010
Sum_{n>=1} 1/a(n) = A215941. - Amiram Eldar, Nov 17 2020

Edited by Dean Hickerson, Feb 15 2002

A067965 Number of binary arrangements without adjacent 1's on n X n array connected ne-sw and nw-se.

Original entry on oeis.org

2, 9, 119, 2704, 177073, 21836929, 6985036032, 4576976735769, 7263963336910751, 24830487842030082304, 198126078679714777857441, 3494153303407491549112098721, 141264727800378056245286463971328, 12779122891585386852029424628087941481, 2628141044813862018744988536642011269669959

Offset: 1

R. H. Hardin, Feb 02 2002

			Neighbors for n=4 (dots represent spaces):
. o..o..o..o
...\/ \/ \/
.../\ /\ /\
. o..o..o..o
...\/ \/ \/
.../\ /\ /\
. o..o..o..o
...\/ \/ \/
.../\ /\ /\
. o..o..o..o

Liang Kai, Table of n, a(n) for n = 1..27 (first 19 terms from Vaclav Kotesovec)
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 69, 417.

Main diagonal of A181212.
Cf. circle A000204, line A000045, arrays: e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw nw-se A067960, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.
Cf. A201861, A212271.

Term a(14) from Vaclav Kotesovec, Dec 06 2011
Term a(15) from Vaclav Kotesovec, Jan 03 2012
Term a(16) from Vaclav Kotesovec, May 01 2012
Term a(17)-a(18) from Vaclav Kotesovec, Aug 13 2016

A067960 Number of binary arrangements without adjacent 1's on n X n torus connected ne-sw nw-se.

Original entry on oeis.org

1, 9, 34, 961, 25531, 2722500, 464483559, 224546142769, 215560806324388, 509113406167679889, 2590618817013278596997, 30737628149641669227004804, 809724336154415150287031740151, 48754690373355654118816600200711441

Offset: 1

R. H. Hardin, Feb 02 2002

If n is odd then A067960(n) = A027683(n).
a(18) = 2184710661251680812138610069332410066909052859790416601664. (a(17) = ?) - Vaclav Kotesovec, Sep 16 2014
a(20) = 61548416926224234005237372092957872593295040887178016957765412173582481. - Vaclav Kotesovec, May 18 2021

			Neighbors for n=4 (dots represent spaces):
.  \ /\ /\ /\ /
.   o..o..o..o
.  / \/ \/ \/ \
.  \ /\ /\ /\ /
.   o..o..o..o
.  / \/ \/ \/ \
.  \ /\ /\ /\ /
.   o..o..o..o
.  / \/ \/ \/ \
.  \ /\ /\ /\ /
.   o..o..o..o
.  / \/ \/ \/ \

Vaclav Kotesovec, Table of n, a(n) for n = 1..16
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 440.

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.

Cf. A212271.

Terms a(12)-a(16) from Vaclav Kotesovec, May 18 2012

A067962 a(n) = F(n+2)*(Product_{i=1..n+1} F(i))^2 where F(i)=A000045(i) is the i-th Fibonacci number.

Original entry on oeis.org

1, 2, 12, 180, 7200, 748800, 204422400, 145957593600, 272940700032000, 1336044726656640000, 17122749216831498240000, 574502481723130428948480000, 50464872497041500009263431680000, 11605406728144633757130311383449600000

Offset: 0

R. H. Hardin, Feb 02 2002

Number of binary arrangements without adjacent 1's on n X n array connected nw-se.

Kitaev and Mansour give a general formula for the number of binary m X n matrices avoiding certain configurations.

			Neighbors for n=4 (dots represent spaces, circles represent grid points):
O..O..O..O
.\..\..\..
..\..\..\.
O..O..O..O
.\..\..\..
..\..\..\.
O..O..O..O
.\..\..\..
..\..\..\.
O..O..O..O

Reinhard Zumkeller, Table of n, a(n) for n = 0..68
Sergey Kitaev and Toufik Mansour, The problem of the pawns, arXiv:math/0305253 [math.CO], 2003; Annals of Combinatorics 8 (2004) 81-91.
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 69, 421.

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, toruses: bare A002416, ne-sw nw-se A067960, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.

Cf. A001654, A003266.

a067962 n = a067962_list !! n
a067962_list = 1 : zipWith (*) a067962_list (drop 2 a001654_list)
-- Reinhard Zumkeller, Sep 24 2015

a:= proc(n) option remember; `if`(n=0, 1, (F->
      F(n+1)*F(n+2)*a(n-1))(combinat[fibonacci]))
    end:
seq(a(n), n=0..14);  # Alois P. Heinz, May 20 2019

Rest[Table[With[{c=Fibonacci[Range[n]]},(Times@@Most[c])^2 Last[c]],{n,15}]] (* Harvey P. Dale, Dec 17 2013 *)

a(n)=fibonacci(n+2)*prod(i=0,n,fibonacci(i+1))^2

a(n) = (F(3) * F(4) * ... * F(n+1))^2 * F(n+2), where F(n) = A000045(n) is the n-th Fibonacci number.
a(n) is asymptotic to C^2*((1+sqrt(5))/2)^((n+2)^2)/(5^(n+3/2)) where C=1.226742010720353244... is the Fibonacci Factorial Constant, see A062073. - Vaclav Kotesovec, Oct 28 2011
a(n) = a(n-1) * A001654(n+1), n > 0. - Reinhard Zumkeller, Sep 24 2015

Edited by Dean Hickerson, Feb 15 2002

Revised by N. J. A. Sloane following comments from Benoit Cloitre, Nov 12 2003

A067958 Number of binary arrangements without adjacent 1's on n X n torus connected e-w ne-sw n-s nw-se.

Original entry on oeis.org

1, 5, 10, 133, 1411, 42938, 1796859, 157763829, 22909432780, 6291183426165, 3032485231813445, 2674030233698391466, 4216437656471537450175, 12038380931111061789962901, 61810608197507432888286102310, 572863067272579464080483552434421

Offset: 1

R. H. Hardin, Feb 02 2002

For n > 1, a(n) is also the number of ways to populate an n X n toroidal chessboard with non-attacking kings (including the case of zero kings). - Vaclav Kotesovec, Oct 10 2011

			Neighbors for n=4:
  :\|/\|/\|/\|/
  :-o--o--o--o-
  :/|\/|\/|\/|\
  :\|/\|/\|/\|/
  :-o--o--o--o-
  :/|\/|\/|\/|\
  :\|/\|/\|/\|/
  :-o--o--o--o-
  :/|\/|\/|\/|\
  :\|/\|/\|/\|/
  :-o--o--o--o-
  :/|\/|\/|\/|\

V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 214.

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw nw-se A067960, ne-sw n-s nw-se A067959, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.

Cf. A212269.

a(14) from Vaclav Kotesovec, Aug 22 2016

a(15)-a(16) from Vaclav Kotesovec, May 15 2021

A067963 Number of binary arrangements without adjacent 1's on n X n array connected e-w ne-sw nw-se.

Original entry on oeis.org

2, 7, 77, 1152, 56549, 3837761, 806190208, 251170142257, 223733272186825, 319544298135448960, 1210302996752248488817, 7876274672755293629849313, 127662922218147601317696761088, 3758866349549535184419575245899295

Offset: 1

R. H. Hardin, Feb 02 2002

			Neighbors for n=4 (dots represent spaces):
. o--o--o--o
...\/ \/ \/
.../\ /\ /\
. o--o--o--o
...\/ \/ \/
.../\ /\ /\
. o--o--o--o
...\/ \/ \/
.../\ /\ /\
. o--o--o--o

R. H. Hardin and Vaclav Kotesovec, Table of n, a(n) for n = 1..30
V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 69-71.

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw nw-se A067960, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.

Diagonal of A228683

Terms a(15)-a(19) from Vaclav Kotesovec, May 01 2012

cp's OEIS Frontend

A006506 Number of n X n binary matrices with no 2 adjacent 1's, or number of configurations of non-attacking princes on an n X n board, where a "prince" attacks the four adjacent (non-diagonal) squares. Also number of independent vertex sets in an n X n grid.

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A066864 Number of binary arrangements without adjacent 1's on n X n rhombic hexagonal grid.

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A067966 Number of binary arrangements without adjacent 1's on n X n array connected n-s.

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A066866 Number of binary arrangements without adjacent 1's in n X n rhombic hexagonal grid torus.

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A067961 Number of binary arrangements without adjacent 1's on n X n torus connected n-s.

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A067965 Number of binary arrangements without adjacent 1's on n X n array connected ne-sw and nw-se.

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A067960 Number of binary arrangements without adjacent 1's on n X n torus connected ne-sw nw-se.

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