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A201373 Number of n X 6 0..1 arrays with rows and columns lexicographically nondecreasing read forwards, and nonincreasing read backwards. 1
2, 7, 32, 157, 786, 3739, 15574, 55410, 170616, 465037, 1145954, 2597729, 5492076, 10947133, 20749996, 37660122, 65814022, 111254955, 182614908, 291980013, 455974718, 697104503, 1045401722, 1540424266, 2233662188, 3191413217 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 6 of A201375.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = (1/453600)*n^10 + (1/2160)*n^9 + (227/60480)*n^8 - (73/1260)*n^7 + (1319/10800)*n^6 + (757/720)*n^5 - (881131/181440)*n^4 + (2207/540)*n^3 + (396407/25200)*n^2 - (6737/210)*n + 18.

Conjectures from Colin Barker, May 22 2018: (Start)

G.f.: x*(2 - 15*x + 65*x^2 - 140*x^3 + 324*x^4 - 166*x^5 + 20*x^6 - 349*x^7 + 391*x^8 - 142*x^9 + 18*x^10) / (1 - x)^11.

a(n) = 11*a(n-1) - 55*a(n-2) + 165*a(n-3) - 330*a(n-4) + 462*a(n-5) - 462*a(n-6) + 330*a(n-7) - 165*a(n-8) + 55*a(n-9) - 11*a(n-10) + a(n-11) for n>11.

(End)

EXAMPLE

Some solutions for n=5:

..0..0..0..1..1..1....0..0..0..1..1..1....0..0..0..0..1..1....0..0..1..1..1..1

..1..1..1..0..1..1....1..1..1..0..1..1....0..1..1..1..0..1....0..0..1..1..1..1

..1..1..1..1..0..1....1..1..1..1..0..1....1..0..0..1..0..1....0..1..0..1..1..1

..1..1..1..1..1..0....1..1..1..1..0..1....1..0..0..1..1..0....1..0..0..1..1..1

..1..1..1..1..1..0....1..1..1..1..1..0....1..1..1..0..0..0....1..1..1..0..0..0

CROSSREFS

Cf. A201375.

Sequence in context: A015655 A320682 A047850 * A168494 A181376 A183951

Adjacent sequences:  A201370 A201371 A201372 * A201374 A201375 A201376

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 30 2011

STATUS

approved

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Last modified March 24 06:56 EDT 2019. Contains 321444 sequences. (Running on oeis4.)