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A270851 Number of 2X2X2 triangular 0..n arrays with some element plus some adjacent element totalling n+1, n or n-1 exactly once. 1
0, 0, 6, 24, 66, 120, 198, 288, 402, 528, 678, 840, 1026, 1224, 1446, 1680, 1938, 2208, 2502, 2808, 3138, 3480, 3846, 4224, 4626, 5040, 5478, 5928, 6402, 6888, 7398, 7920, 8466, 9024, 9606, 10200, 10818, 11448, 12102, 12768, 13458, 14160, 14886, 15624 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 2 of A270850.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) -2*a(n-3) +a(n-4) for n>5

Empirical for n mod 2 = 0: a(n) = 9*n^2 - 42*n + 48 for n>1

Empirical for n mod 2 = 1: a(n) = 9*n^2 - 42*n + 51 for n>1

EXAMPLE

Some solutions for n=4

...2....1....0....1....0....4....3....2....2....2....0....4....4....2....3....2

..0.4..2.0..1.2..0.2..2.4..2.0..4.2..4.3..2.0..0.2..2.2..2.2..0.2..0.1..2.4..4.2

CROSSREFS

Cf. A270850.

Sequence in context: A101854 A273358 A101877 * A092348 A274772 A234271

Adjacent sequences:  A270848 A270849 A270850 * A270852 A270853 A270854

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 24 2016

STATUS

approved

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Last modified February 22 19:56 EST 2019. Contains 320403 sequences. (Running on oeis4.)