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A183911 Number of nondecreasing arrangements of n+2 numbers in 0..8 with each number being the sum mod 9 of two others. 1
1, 4, 31, 231, 1093, 3631, 9576, 21660, 43980, 82453, 145376, 244106, 393876, 614764, 932833, 1381461, 2002881, 2849952, 3988183, 5498033, 7477511, 10045101, 13343038, 17540962, 22839978, 29477151, 37730466, 47924284, 60435326, 75699218 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 8 of A183912.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..52

FORMULA

Empirical: a(n) = (1/40320)*n^8 + (13/10080)*n^7 + (83/2880)*n^6 + (13/36)*n^5 + (15967/5760)*n^4 - (45839/1440)*n^3 + (59583/1120)*n^2 + (20743/168)*n - 297 for n>3.

Conjectures from Colin Barker, Apr 06 2018: (Start)

G.f.: x*(1 - 5*x + 31*x^2 + 12*x^3 - 80*x^4 - 116*x^5 + 327*x^6 - 120*x^7 - 147*x^8 + 120*x^9 - 20*x^10 - 2*x^11) / (1 - x)^9.

a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>11.

(End)

EXAMPLE

All solutions for n=2:

..0....0....3....0

..3....0....3....3

..3....0....6....6

..6....0....6....6

CROSSREFS

Cf. A183912.

Sequence in context: A124033 A014537 A136284 * A039765 A001091 A309184

Adjacent sequences:  A183908 A183909 A183910 * A183912 A183913 A183914

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 07 2011

STATUS

approved

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Last modified August 25 03:00 EDT 2019. Contains 326318 sequences. (Running on oeis4.)