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A250810 Number of (n+1) X (6+1) 0..2 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction. 1
1296, 5139, 18537, 62469, 201741, 634509, 1962717, 6007149, 18260061, 55258029, 166730397, 502104429, 1510140381, 4538075949, 13629538077, 40919235309, 122818948701, 368579332269, 1105982969757, 3318438855789, 9956296461021 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3); a(n) = (1904*3^n - 1869*2^n + 618)/2.
Empirical g.f.: 3*x*(432 - 879*x + 653*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Nov 20 2018
EXAMPLE
Some solutions for n=4:
..2..2..2..2..2..2..1....2..2..2..2..2..2..0....2..2..1..1..1..0..0
..1..1..1..1..1..1..1....0..0..0..0..0..0..0....0..0..0..0..0..0..0
..0..0..0..0..1..1..1....2..2..2..2..2..2..2....0..1..1..1..1..1..1
..1..1..1..1..2..2..2....1..1..1..1..1..1..1....0..1..1..1..1..2..2
..0..0..0..1..2..2..2....1..1..2..2..2..2..2....0..1..1..1..1..2..2
CROSSREFS
Column 6 of A250812.
Sequence in context: A372841 A217908 A223508 * A320893 A276282 A137488
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 27 2014
STATUS
approved

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Last modified May 29 22:36 EDT 2024. Contains 372954 sequences. (Running on oeis4.)