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A221540
Number of 0..6 arrays of length n with each element differing from at least one neighbor by something other than 1, starting with 0.
1
0, 6, 32, 222, 1455, 9665, 64047, 424593, 2814515, 18656979, 123673887, 819813575, 5434406883, 36023773275, 238795558499, 1582935756291, 10493015970771, 69556445196155, 461078023878243, 3056408985571563, 20260423189286435
OFFSET
1,2
COMMENTS
Column 6 of A221542.
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) -4*a(n-2) +6*a(n-3) +26*a(n-4) +10*a(n-5) +16*a(n-6) +12*a(n-8).
Empirical g.f.: x^2*(6 - 10*x + 22*x^2 - 7*x^3 + 20*x^4 - 12*x^5 + 6*x^6) / (1 - 7*x + 4*x^2 - 6*x^3 - 26*x^4 - 10*x^5 - 16*x^6 - 12*x^8). - Colin Barker, Oct 18 2017
EXAMPLE
Some solutions for n=6
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..6....5....2....4....5....2....0....0....5....6....3....0....2....0....5....4
..2....2....6....1....2....1....0....6....6....6....5....6....0....4....1....0
..5....2....0....6....2....1....2....2....6....3....1....3....3....3....0....6
..5....6....0....5....6....5....6....0....6....4....5....5....4....1....3....6
..2....6....0....3....0....0....4....4....0....1....3....1....0....6....3....4
CROSSREFS
Sequence in context: A146557 A020013 A283326 * A331878 A121120 A183681
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 19 2013
STATUS
approved