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A194932
Number of lower triangles of a 3 X 3 0..n array with no element differing from any of its horizontal or vertical neighbors by more than one.
1
64, 217, 386, 557, 728, 899, 1070, 1241, 1412, 1583, 1754, 1925, 2096, 2267, 2438, 2609, 2780, 2951, 3122, 3293, 3464, 3635, 3806, 3977, 4148, 4319, 4490, 4661, 4832, 5003, 5174, 5345, 5516, 5687, 5858, 6029, 6200, 6371, 6542, 6713, 6884, 7055, 7226
OFFSET
1,1
COMMENTS
Row 3 of A194931.
LINKS
FORMULA
Empirical: a(n) = 171*n - 127 for n>2.
Empirical g.f.: x*(64 + 89*x + 16*x^2 + 2*x^3) / (1 - x)^2. - Colin Barker, May 05 2018
EXAMPLE
Some solutions for n=4:
..1......0......3......3......1......0......1......3......1......4......3
..2.2....1.2....3.2....3.4....1.1....1.2....0.1....4.3....1.2....3.4....2.2
..3.2.2..2.3.4..2.3.3..3.4.3..2.1.0..1.1.2..0.0.1..4.3.4..0.1.1..2.3.2..3.2.2
CROSSREFS
Cf. A194931.
Sequence in context: A245991 A186637 A295021 * A016994 A258732 A279714
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 05 2011
STATUS
approved