A165380 Number of slanted n X n (i=1..n)X(j=i..n+i-1) 1..4 arrays with all 1s connected, all 2s connected, all 3s connected, all 4s connected, 1 in the upper left corner, 2 in the upper right corner, 3 in the lower left corner, 4 in the lower right corner, and with no element having more than 3 neighbors with the same value

1, 40, 1012, 18900, 598332, 30346872, 3445935988

Offset

2,2

Links

Table of n, a(n) for n=2..8.

Example

Some solutions for n=4
...1.1.1.2.........1.2.2.2.........1.1.1.2.........1.1.4.2......
.....2.2.2.4.........2.2.2.2.........1.1.2.2.........4.4.2.4....
.......2.3.4.4.........3.3.2.4.........1.1.2.4.........4.4.4.4..
.........3.4.4.4.........3.3.4.4.........3.2.4.4.........3.3.4.4
------
...1.2.2.2.........1.2.2.2.........1.1.2.2.........1.1.1.2......
.....3.3.2.2.........3.3.2.4.........2.2.2.2.........2.2.2.2....
.......3.3.2.2.........3.3.4.4.........3.3.2.2.........3.3.3.4..
.........3.2.2.4.........3.3.4.4.........3.3.4.4.........3.3.4.4
------
...1.1.1.2.........1.1.2.2.........1.1.1.2.........1.1.2.2......
.....1.1.2.2.........1.1.3.3.........2.2.2.2.........1.2.2.2....
.......3.3.3.4.........1.3.3.4.........3.3.2.3.........3.3.2.4..
.........3.4.4.4.........3.3.4.4.........3.3.3.4.........3.3.4.4

Crossrefs

Sequence in context: A004349 A016092 A028228 * A075907 A062143 A284838

Adjacent sequences: A165377 A165378 A165379 * A165381 A165382 A165383

Keyword

nonn

Author

R. H. Hardin Sep 17 2009

Status

approved