A167238 Number of ways to partition a 2*n X 2 grid into 4 connected equal-area regions

1, 5, 11, 25, 45, 77, 119, 177, 249, 341, 451, 585, 741, 925, 1135, 1377, 1649, 1957, 2299, 2681, 3101, 3565, 4071, 4625, 5225, 5877, 6579, 7337, 8149, 9021, 9951, 10945, 12001, 13125, 14315, 15577

Offset

1,2

Links

Table of n, a(n) for n=1..36.

Formula

Empirical: a(n)=3*a(n-1)-2*a(n-2)-2*a(n-3)+3*a(n-4)-a(n-5)

Example

All solutions for n=3
...1.1...1.1...1.1...1.1...1.1...1.1...1.1...1.1...1.2...1.2...1.2
...1.2...1.2...1.2...1.2...2.1...2.1...2.1...2.1...1.2...1.2...1.2
...2.2...2.2...2.2...3.2...2.2...2.2...2.2...2.3...1.2...1.2...1.2
...3.3...3.3...3.4...3.2...3.3...3.3...3.4...2.3...3.3...3.3...3.4
...3.4...4.3...3.4...3.4...3.4...4.3...3.4...4.3...3.4...4.3...3.4
...4.4...4.4...3.4...4.4...4.4...4.4...3.4...4.4...4.4...4.4...3.4

Crossrefs

Sequence in context: A266905 A059358 A296911 * A084640 A337481 A056739

Adjacent sequences: A167235 A167236 A167237 * A167239 A167240 A167241

Keyword

nonn

Author

R. H. Hardin Oct 31 2009

Status

approved