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A270608 Number of 3X3X3 triangular 0..n arrays with some element plus some adjacent element totalling n+1 or n-1 exactly once. 1
0, 0, 312, 1716, 8148, 23448, 67788, 144252, 315936, 568032, 1049532, 1692228, 2793240, 4176936, 6369012, 9014028, 12965136, 17596272, 24205356, 31786452, 42217992, 53986488, 69705060, 87206556, 110011392, 135134208, 167193756 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 3 of A270606.

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) = 18*n^5 - 216*n^4 + 1296*n^3 - 4464*n^2 + 8562*n - 7188 for n>7

Empirical for n mod 2 = 1: a(n) = 18*n^5 - 216*n^4 + 1392*n^3 - 5532*n^2 + 13068*n - 14058 for n>7

EXAMPLE

Some solutions for n=4

....3......4......1......3......1......1......4......3......3......4......3

...4.3....4.0....1.0....3.4....3.3....2.0....2.3....3.3....2.4....4.4....4.0

..0.3.1..3.3.1..0.1.3..3.1.3..0.1.3..4.2.0..2.4.3..2.4.3..0.2.4..2.3.3..0.0.0

CROSSREFS

Cf. A270606.

Sequence in context: A011251 A043360 A237551 * A233939 A233934 A289793

Adjacent sequences:  A270605 A270606 A270607 * A270609 A270610 A270611

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 20 2016

STATUS

approved

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Last modified July 15 23:32 EDT 2020. Contains 335774 sequences. (Running on oeis4.)