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A222156 Number of nX4 arrays with each row a permutation of 1..4 having at least as many downsteps as the preceding row, with rows in lexicographically nondecreasing order 1
24, 277, 2132, 12521, 60344, 249641, 913748, 3023603, 9190984, 25981835, 68967340, 173242095, 414433320, 949144335, 2090284620, 4443280530, 9145850640, 18279915390, 35563612920, 67490348310, 125168633040, 227242504470 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 4 of A222159

LINKS

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

FORMULA

Empirical: a(n) = (1/3201186852864000)*n^18 + (1/19760412672000)*n^17 + (251/62768369664000)*n^16 + (29/145297152000)*n^15 + (217031/31384184832000)*n^14 + (43447/249080832000)*n^13 + (2169611/658409472000)*n^12 + (3183331/67060224000)*n^11 + (231419681/438939648000)*n^10 + (36901183/8128512000)*n^9 + (146423897891/4828336128000)*n^8 + (1499409367/9580032000)*n^7 + (14551383635479/23538138624000)*n^6 + (400802254661/217945728000)*n^5 + (5254041870533/1307674368000)*n^4 + (112591393237/18162144000)*n^3 + (17776195417/2806876800)*n^2 + (46566643/12252240)*n + 1

EXAMPLE

Some solutions for n=3

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

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

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

CROSSREFS

Sequence in context: A014809 A007191 A097340 * A297604 A001496 A055754

Adjacent sequences:  A222153 A222154 A222155 * A222157 A222158 A222159

KEYWORD

nonn

AUTHOR

R. H. Hardin Feb 10 2013

STATUS

approved

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Last modified November 20 05:07 EST 2019. Contains 329323 sequences. (Running on oeis4.)