

A246473


Number of length n+3 0..2 arrays with no pair in any consecutive four terms totalling exactly 2.


2



10, 14, 20, 28, 38, 52, 72, 100, 138, 190, 262, 362, 500, 690, 952, 1314, 1814, 2504, 3456, 4770, 6584, 9088, 12544, 17314, 23898, 32986, 45530, 62844, 86742, 119728, 165258, 228102, 314844, 434572, 599830, 827932, 1142776, 1577348, 2177178
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OFFSET

1,1


COMMENTS



LINKS



FORMULA

Empirical: a(n) = a(n1) + a(n4).
Empirical g.f.: 2*x*(5 + 2*x + 3*x^2 + 4*x^3) / (1  x  x^4).  Colin Barker, Mar 19 2018


EXAMPLE

Some solutions for n=6:
..2....0....2....2....1....0....1....0....2....1....2....1....0....0....0....1
..2....0....2....2....0....0....2....0....2....0....1....2....0....1....0....2
..2....0....1....2....0....0....2....1....2....0....2....2....0....0....0....2
..2....0....2....2....0....1....2....0....1....0....2....2....1....0....0....2
..2....0....2....2....0....0....2....0....2....0....2....1....0....0....0....2
..2....0....2....2....0....0....1....0....2....1....2....2....0....0....0....2
..2....0....2....2....0....0....2....0....2....0....2....2....0....0....0....2
..1....0....2....2....1....0....2....0....2....0....1....2....1....1....0....2
..2....0....2....1....0....0....2....0....1....0....2....1....0....0....1....2


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



