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A245991
Number of length n+2 0..4 arrays with no pair in any consecutive three terms totalling exactly 4.
1
64, 208, 676, 2196, 7132, 23168, 75260, 244464, 794096, 2579500, 8379052, 27217860, 88412560, 287192948, 932896352, 3030352272, 9843575108, 31975148500, 103865731612, 337389844512, 1095952482460, 3560011839440, 11564081956784
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-2) + 9*a(n-3) + 3*a(n-4).
Empirical g.f.: 4*x*(16 + 20*x + 49*x^2 + 15*x^3) / (1 - 2*x - x^2 - 9*x^3 - 3*x^4). - Colin Barker, Nov 05 2018
EXAMPLE
Some solutions for n=7:
3 3 4 0 2 2 3 2 2 3 4 3 4 0 4 0
4 4 1 3 1 1 4 3 4 2 2 0 1 3 2 1
4 4 1 0 1 1 3 4 4 3 4 2 2 2 1 1
4 2 2 2 0 4 4 3 2 3 3 0 0 3 4 2
3 4 0 0 2 2 3 3 1 0 2 1 3 4 4 4
3 3 0 3 0 1 2 3 4 0 4 2 3 3 3 4
2 3 0 0 1 1 0 0 2 2 1 1 0 2 4 4
4 0 3 0 1 2 3 0 1 3 2 4 2 3 4 4
4 0 2 1 1 4 0 3 0 4 1 1 1 0 2 4
CROSSREFS
Column 4 of A245995.
Sequence in context: A250135 A273321 A091077 * A186637 A295021 A194932
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 09 2014
STATUS
approved