A323861 Table read by antidiagonals where A(n,k) is the number of n X k aperiodic binary toroidal necklaces.
2, 1, 1, 2, 2, 2, 3, 9, 9, 3, 6, 27, 54, 27, 6, 9, 99, 335, 335, 99, 9, 18, 326, 2182, 4050, 2182, 326, 18, 30, 1161, 14523, 52377, 52377, 14523, 1161, 30, 56, 4050, 99858, 698535, 1342170, 698535, 99858, 4050, 56, 99, 14532, 698870, 9586395, 35790267, 35790267, 9586395, 698870, 14532, 99
Offset: 1
Examples
Table begins: 1 2 3 4 ------------------------ 1: | 2 1 2 3 2: | 1 2 9 27 3: | 2 9 54 335 4: | 3 27 335 4050 Inequivalent representatives of the A(3,2) = 9 aperiodic toroidal necklaces: [0 0 0] [0 0 0] [0 0 1] [0 0 1] [0 0 1] [0 0 1] [0 0 1] [0 1 1] [0 1 1] [0 0 1] [0 1 1] [0 1 0] [0 1 1] [1 0 1] [1 1 0] [1 1 1] [1 0 1] [1 1 1]
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..1275
- S. N. Ethier, Counting toroidal binary arrays, J. Int. Seq. 16 (2013) #13.4.7.
- Andrew Howroyd, GAP Program Code
Crossrefs
Programs
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GAP
# See link for code. for n in [1..8] do for k in [1..8] do Print(A323861(n,k), ", "); od; Print("\n"); od; # Andrew Howroyd, Aug 21 2019
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Mathematica
apermatQ[m_]:=UnsameQ@@Join@@Table[RotateLeft[m,{i,j}],{i,Length[m]},{j,Length[First[m]]}]; neckmatQ[m_]:=m==First[Union@@Table[RotateLeft[m,{i,j}],{i,Length[m]},{j,Length[First[m]]}]]; Table[Length[Select[Partition[#,n-k]&/@Tuples[{0,1},(n-k)*k],And[apermatQ[#],neckmatQ[#]]&]],{n,6},{k,n-1}]
Extensions
Terms a(37) and beyond from Andrew Howroyd, Aug 21 2019
Comments