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A167238
Number of ways to partition a 2*n X 2 grid into 4 connected equal-area regions
0
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
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 * A376763 A084640 A337481
KEYWORD
nonn
AUTHOR
R. H. Hardin Oct 31 2009
STATUS
approved