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A270511 Number of 3X3X3 triangular 0..n arrays with some element plus some adjacent element totalling n+1 exactly once. 1
15, 144, 1137, 4584, 15843, 40392, 95109, 189936, 362487, 625440, 1048665, 1643544, 2526027, 3699864, 5343213, 7443552, 10259679, 13751856, 18280257, 23764680, 30689715, 38919144, 49087317, 60984144, 75421383, 92094912, 112023849 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Row 3 of A270509.
LINKS
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)
Empirical for n mod 2 = 0: a(n) = 9*n^5 - 36*n^4 + 96*n^3 - 111*n^2 + 54*n
Empirical for n mod 2 = 1: a(n) = 9*n^5 - 36*n^4 + 108*n^3 - 156*n^2 + 132*n - 42
EXAMPLE
Some solutions for n=4
....4......1......3......2......1......0......3......1......2......0......3
...3.2....4.0....3.3....4.1....3.3....3.1....4.1....3.0....2.1....2.0....3.4
..3.0.1..3.3.4..0.1.4..3.3.0..2.0.3..4.1.3..4.0.1..0.2.0..4.4.2..0.3.3..3.1.3
CROSSREFS
Cf. A270509.
Sequence in context: A240158 A255944 A243418 * A026893 A368075 A163799
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 18 2016
STATUS
approved

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Last modified July 16 15:16 EDT 2024. Contains 374349 sequences. (Running on oeis4.)