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A222002 Number of n X 4 arrays with each row a permutation of 1..4 having at least as many downsteps as the preceding row, with rows in lexicographically nonincreasing order. 1
24, 157, 704, 2470, 7328, 19228, 45894, 101543, 211070, 416275, 784864, 1423138, 2493494, 4238102, 7010394, 11316307, 17867564, 27649657, 42007616, 62753110, 92296932, 133811472, 191428382, 270477287, 377772098, 521952239, 713886912 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 4 of A222005.

LINKS

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

FORMULA

Empirical: 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).

Empirical g.f.: x*(24 - 107*x + 297*x^2 - 599*x^3 + 893*x^4 - 968*x^5 + 750*x^6 - 405*x^7 + 145*x^8 - 31*x^9 + 3*x^10) / (1 - x)^11. - Colin Barker, Aug 14 2018

EXAMPLE

Some solutions for n=3:

..2..1..3..4....2..3..1..4....4..1..2..3....3..2..1..4....4..1..3..2

..1..4..2..3....2..1..3..4....2..4..1..3....3..2..1..4....3..2..4..1

..1..3..2..4....1..4..2..3....2..3..1..4....3..1..4..2....2..1..4..3

CROSSREFS

Cf. A222005.

Sequence in context: A277984 A125334 A126492 * A240268 A231341 A186862

Adjacent sequences:  A221999 A222000 A222001 * A222003 A222004 A222005

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 03 2013

STATUS

approved

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Last modified January 26 16:03 EST 2022. Contains 350599 sequences. (Running on oeis4.)