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A270852 Number of 3X3X3 triangular 0..n arrays with some element plus some adjacent element totalling n+1, n or n-1 exactly once. 1
0, 0, 30, 270, 1650, 7344, 24954, 68838, 164454, 347916, 677130, 1219626, 2083038, 3373728, 5268642, 7918158, 11590422, 16482708, 22978554, 31322706, 42040590, 55422696, 72165138, 92600118, 117625542, 147608988, 183683562, 226243578 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 3 of A270850.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) +3*a(n-2) -8*a(n-3) -2*a(n-4) +12*a(n-5) -2*a(n-6) -8*a(n-7) +3*a(n-8) +2*a(n-9) -a(n-10) for n>17

Empirical for n mod 2 = 0: a(n) = 27*n^5 - 531*n^4 + 4794*n^3 - 24417*n^2 + 69189*n - 86274 for n>7

Empirical for n mod 2 = 1: a(n) = 27*n^5 - 531*n^4 + 4806*n^3 - 24624*n^2 + 70425*n - 88833 for n>7

EXAMPLE

Some solutions for n=4

....4......0......4......4......2......2......1......2......0......2......2

...3.4....0.1....4.4....4.4....0.0....1.0....1.0....2.0....2.2....1.0....4.4

..2.4.3..0.2.0..3.2.4..2.2.4..0.2.1..1.0.0..2.0.0..0.0.2..0.0.0..1.1.0..4.3.2

CROSSREFS

Cf. A270850.

Sequence in context: A163667 A214944 A259455 * A229427 A113754 A129029

Adjacent sequences:  A270849 A270850 A270851 * A270853 A270854 A270855

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 24 2016

STATUS

approved

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Last modified January 22 23:50 EST 2022. Contains 350504 sequences. (Running on oeis4.)