A165393 Number of slanted 3Xn (i=1..3)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 2 neighbors with the same value

3, 28, 94, 154, 233, 300, 370, 428, 491, 552, 614, 676, 738, 800, 862, 924, 986, 1048, 1110, 1172, 1234, 1296, 1358, 1420, 1482, 1544, 1606, 1668, 1730, 1792, 1854, 1916, 1978, 2040, 2102, 2164, 2226

Offset

2,1

Links

Table of n, a(n) for n=2..38.

Formula

Empirical: a(n)=2*a(n-1)-a(n-2) for n>=13

Example

Some solutions for n=4
...1.1.3.2.......1.2.2.2.......1.2.2.2.......1.3.2.2.......1.1.3.2....
.....1.3.2.2.......3.3.4.4.......2.4.4.4.......3.3.4.4.......1.3.2.3..
.......3.3.2.4.......3.3.4.4.......3.3.4.4.......3.3.4.4.......3.3.3.4
------
...1.1.3.2.......1.1.1.2.......1.1.2.2.......1.1.2.2.......1.1.1.2....
.....1.3.2.2.......3.3.2.4.......1.1.2.4.......1.3.2.2.......3.3.4.4..
.......3.3.3.4.......3.2.4.4.......3.3.4.4.......3.3.4.4.......3.3.4.4
------
...1.2.2.2.......1.1.2.2.......1.1.1.2.......1.1.2.2.......1.1.3.2....
.....3.3.2.4.......1.2.2.3.......2.2.2.4.......1.3.2.2.......1.3.4.4..
.......3.2.4.4.......3.3.3.4.......3.3.4.4.......3.3.3.4.......3.3.4.4

Crossrefs

Sequence in context: A229055 A061793 A186429 * A107651 A239057 A338791

Adjacent sequences: A165390 A165391 A165392 * A165394 A165395 A165396

Keyword

nonn

Author

R. H. Hardin Sep 17 2009

Status

approved