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A292357
Array read by antidiagonals: T(m,n) is the number of fixed polyominoes that have a width of m and height of n.
11
1, 1, 1, 1, 5, 1, 1, 15, 15, 1, 1, 39, 111, 39, 1, 1, 97, 649, 649, 97, 1, 1, 237, 3495, 7943, 3495, 237, 1, 1, 575, 18189, 86995, 86995, 18189, 575, 1, 1, 1391, 93231, 910667, 1890403, 910667, 93231, 1391, 1
OFFSET
1,5
COMMENTS
Equivalently, the number of m X n binary arrays with all 1's connected and at least one 1 on each edge.
FORMULA
T(m, n) = U(m, n) - 2*U(m, n-1) + U(m, n-2) where U(m, n) = V(m, n) - 2*V(m-1, n) + V(m-2, n) and V(m, n) = A287151(m, n).
EXAMPLE
Array begins:
===============================================================
m\n| 1 2 3 4 5 6 7
---|-----------------------------------------------------------
1 | 1 1 1 1 1 1 1...
2 | 1 5 15 39 97 237 575...
3 | 1 15 111 649 3495 18189 93231...
4 | 1 39 649 7943 86995 910667 9339937...
5 | 1 97 3495 86995 1890403 38916067 782256643...
6 | 1 237 18189 910667 38916067 1562052227 61025668579...
7 | 1 575 93231 9339937 782256643 61025668579 4617328590967...
...
T(2,2) = 5 counts 4 3-ominoes of shape 2x2 and 1 4-omino of shape 2x2.
T(3,2) = 15 counts 8 4-ominoes of shape 3x2, 6 5-ominoes of shape 3x2, and 1 6-omino of shape 3x2.
T(4,2) = 39 counts 12 5-ominoes of shape 4x2, 18 6-ominoes of shape 4x2, 8 7-ominoes of shape 4x2, and 1 8-omino of shape 4x2.
MATHEMATICA
A287151 = Import["https://oeis.org/A287151/b287151.txt", "Table"][[All, 2]];
imax = Length[A287151];
mmax = Sqrt[2 imax] // Ceiling;
Clear[V]; VV = Table[V[m-n+1, n], {m, 1, mmax}, {n, 1, m}] // Flatten;
Do[Evaluate[VV[[i]]] = A287151[[i]], {i, 1, imax}];
V[0, _] = V[_, 0] = 0;
T[m_, n_] := If[m == 1 || n == 1, 1, U[m, n] - 2 U[m, n-1] + U[m, n-2]];
U[m_, n_] := V[m, n] - 2 V[m-1, n] + V[m-2, n];
Table[T[m-n+1, n], {m, 1, mmax}, {n, 1, m}] // Flatten // Take[#, imax]& (* Jean-François Alcover, Sep 22 2019 *)
CROSSREFS
Rows 2..4 are A034182, A034184, A034187.
Main diagonal is A268404.
Cf. A268371 (nonequivalent), A287151, A308359.
Sequence in context: A157147 A347973 A232103 * A156920 A174044 A174159
KEYWORD
nonn,tabl
AUTHOR
Andrew Howroyd, Oct 02 2017
STATUS
approved