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A246482 Number of length 3+3 0..n arrays with no pair in any consecutive four terms totalling exactly n. 1
2, 20, 292, 1376, 6534, 20004, 57416, 133664, 293770, 574100, 1073772, 1865280, 3134222, 5007716, 7797904, 11708864, 17227026, 24659604, 34722740, 47856800, 65070742, 86971940, 114932952, 149765856, 193285274, 246549524, 311901436 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) - 11*a(n-3) + 6*a(n-4) + 14*a(n-5) - 14*a(n-6) - 6*a(n-7) + 11*a(n-8) - a(n-9) - 3*a(n-10) + a(n-11).
Conjectures from Colin Barker, Nov 06 2018: (Start)
G.f.: 2*x*(1 + 7*x + 115*x^2 + 251*x^3 + 1161*x^4 + 1045*x^5 + 2001*x^6 + 617*x^7 + 562*x^8) / ((1 - x)^7*(1 + x)^4).
a(n) = -20*n + 43*n^2 - 40*n^3 + 21*n^4 - 6*n^5 + n^6 for n even.
a(n) = -26 + 37*n + 5*n^2 - 30*n^3 + 21*n^4 - 6*n^5 + n^6 for n odd.
(End)
EXAMPLE
Some solutions for n=6:
..3....6....2....5....5....3....1....6....6....4....2....6....1....1....1....5
..4....4....2....3....5....5....0....1....4....4....1....2....2....2....6....2
..1....5....2....5....3....5....3....3....6....4....6....5....0....6....2....6
..0....3....2....6....2....6....4....1....3....4....6....2....3....2....3....5
..3....0....2....6....2....4....0....2....4....4....6....6....2....1....5....5
..2....5....6....5....1....3....0....2....6....1....3....6....1....3....0....6
CROSSREFS
Row 3 of A246479.
Sequence in context: A326010 A363380 A349963 * A124211 A277308 A128481
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 27 2014
STATUS
approved

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Last modified March 2 14:45 EST 2024. Contains 370493 sequences. (Running on oeis4.)