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Revision History for A201975 (Bold, blue-underlined text is an addition; faded, red-underlined text is a deletion.)

Showing all changes.
A201975
Number of n X 2 0..3 arrays with rows and columns lexicographically nondecreasing read forwards and nonincreasing read backwards.
(history; published version)
#9 by Joerg Arndt at Fri May 25 11:14:01 EDT 2018
STATUS

reviewed

approved

#8 by Michel Marcus at Fri May 25 10:49:15 EDT 2018
STATUS

proposed

reviewed

#7 by Colin Barker at Fri May 25 10:44:52 EDT 2018
STATUS

editing

proposed

#6 by Colin Barker at Fri May 25 10:44:29 EDT 2018
NAME

Number of nX2 n X 2 0..3 arrays with rows and columns lexicographically nondecreasing read forwards and nonincreasing read backwards.

COMMENTS

Column 2 of A201981.

FORMULA

Empirical: a(n) = (1/6)*n^3 + 7*n^2 + (23/6)*n - 7.

Conjectures from Colin Barker, May 25 2018: (Start)

G.f.: x*(4 + 14*x - 24*x^2 + 7*x^3) / (1 - x)^4.

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.

(End)

EXAMPLE

Some solutions for n=9.

CROSSREFS

Cf. A201981.

AUTHOR

R. H. Hardin , Dec 07 2011

STATUS

approved

editing

#5 by Russ Cox at Sat Mar 31 12:36:45 EDT 2012
AUTHOR

_R. H. Hardin (rhhardin(AT)att.net) _ Dec 07 2011

Discussion
Sat Mar 31
12:36
OEIS Server: https://oeis.org/edit/global/875
#4 by Ron Hardin at Wed Dec 07 06:48:28 EST 2011
STATUS

editing

approved

#3 by Ron Hardin at Wed Dec 07 06:48:24 EST 2011
LINKS

R. H. Hardin, <a href="/A201975/b201975.txt">Table of n, a(n) for n = 1..210</a>

#2 by Ron Hardin at Wed Dec 07 06:47:56 EST 2011
NAME

allocated for Ron HardinNumber of nX2 0..3 arrays with rows and columns lexicographically nondecreasing read forwards and nonincreasing read backwards

DATA

4, 30, 72, 131, 208, 304, 420, 557, 716, 898, 1104, 1335, 1592, 1876, 2188, 2529, 2900, 3302, 3736, 4203, 4704, 5240, 5812, 6421, 7068, 7754, 8480, 9247, 10056, 10908, 11804, 12745, 13732, 14766, 15848, 16979, 18160, 19392, 20676, 22013, 23404, 24850

OFFSET

1,1

COMMENTS

Column 2 of A201981

FORMULA

Empirical: a(n) = (1/6)*n^3 + 7*n^2 + (23/6)*n - 7

EXAMPLE

Some solutions for n=9

..0..3....1..3....0..3....0..3....1..3....0..3....0..3....1..2....0..3....0..1

..0..3....1..3....0..3....0..3....2..2....0..3....1..2....3..1....0..3....3..0

..1..2....1..3....0..3....0..3....2..2....0..3....1..2....3..1....1..2....3..0

..1..2....1..3....0..3....0..3....2..2....0..3....1..2....3..1....2..1....3..0

..1..2....1..3....2..0....0..3....2..2....2..1....1..2....3..1....2..1....3..0

..2..0....1..3....2..0....1..2....2..2....2..1....1..2....3..1....2..1....3..0

..2..0....2..2....2..0....1..2....2..2....2..1....1..2....3..1....3..0....3..0

..2..0....3..1....2..0....1..2....3..0....2..1....3..1....3..1....3..0....3..0

..2..0....3..1....2..0....2..1....3..0....2..1....3..1....3..1....3..0....3..0

KEYWORD

allocated

nonn

AUTHOR

R. H. Hardin (rhhardin(AT)att.net) Dec 07 2011

STATUS

approved

editing

#1 by Ron Hardin at Wed Dec 07 06:44:31 EST 2011
NAME

allocated for Ron Hardin

KEYWORD

allocated

STATUS

approved

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