A270851 Number of 2X2X2 triangular 0..n arrays with some element plus some adjacent element totalling n+1, n or n-1 exactly once.

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

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: A325517 A344508 A101877 * A092348 A274772 A369177

Adjacent sequences: A270848 A270849 A270850 * A270852 A270853 A270854

Keyword

nonn

Author

R. H. Hardin, Mar 24 2016

Status

approved