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A264872 Array read by antidiagonals: T(n,m) = 2^n*(1+2^n)^m; n,m >= 0. 0
1, 2, 2, 4, 6, 4, 8, 18, 20, 8, 16, 54, 100, 72, 16, 32, 162, 500, 648, 272, 32, 64, 486, 2500, 5832, 4624, 1056, 64, 128, 1458, 12500, 52488, 78608, 34848, 4160, 128, 256, 4374, 62500, 472392, 1336336, 1149984, 270400, 16512, 256, 512, 13122, 312500 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Start with an n X m rectangle and cut it vertically along any set of the m-1 separators. There are binomial(m-1,c) ways of doing this with 0 <= c < m cuts. Inside each of these 1+c regions cut vertically, for which there are 2^(n-1) choices. The total number of ways of dissecting the rectangle into rectangles in this way is Sum_{c=0..m-1} binomial(m-1,c) 2^((1+c)(n-1)) = 2^(n-1)*(1+2^(n-1))^(m-1) = T(n-1,m-1).

The symmetrized version of the array is S(n,m) = T(n,m) + T(m,n) - 2^(m+n) <= A116694(n,m), which counts tilings that start with guillotine cuts either horizontally or vertically, avoiding double counting of the tilings where the order of the cuts does not matter. - R. J. Mathar, Nov 29 2015

LINKS

Table of n, a(n) for n=0..47.

R. J. Mathar, Counting 2-way monotonic terrace forms over rectangular landscapes, vixra:1511.0225 (2015), Section 6.

FORMULA

T(n,m) = 2^n*A264871(n,m).

T(n,m) <= A116694(n+1,m+1).

EXAMPLE

   1,    2,     4,       8,       16,         32, ...

   2,    6,    18,      54,      162,        486, ...

   4,   20,   100,     500,     2500,      12500, ...

   8,   72,   648,    5832,    52488,     472392, ...

  16,  272,  4624,   78608,  1336336,   22717712, ...

  32, 1056, 34848, 1149984, 37949472, 1252332576, ...

.

The symmetrized version S(n,m) starts

   1,    2,     4,       8,       16,         32, ...

   2,    8,    30,     110,      402,       1478, ...

   4,   30,   184,    1116,     7060,      47220, ...

   8,  110,  1116,   11600,   130968,    1622120, ...

  16,  402,  7060,  130968,  2672416,   60666672, ...

  32, 1478, 47220, 1622120, 60666672, 2504664128, ...

MATHEMATICA

Table[2^(n - m) (1 + 2^(n - m))^m, {n, 9}, {m, 0, n}] // Flatten (* Michael De Vlieger, Nov 27 2015 *)

CROSSREFS

Cf. A000079 (row and column 0), A008776 (row 1), A005054 (row 2), A055275 (row 3), A063376 (column 1).

Sequence in context: A252828 A208314 A078099 * A303306 A347797 A118960

Adjacent sequences:  A264869 A264870 A264871 * A264873 A264874 A264875

KEYWORD

nonn,tabl,easy

AUTHOR

R. J. Mathar, Nov 27 2015

STATUS

approved

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Last modified December 4 15:36 EST 2021. Contains 349526 sequences. (Running on oeis4.)