OFFSET
1,2
COMMENTS
Every 0 is next to 0 2's, every 1 is next to 1 3, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 4's.
Column 4 of A196746.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
Robert Israel, Maple-assisted proof of empirical formula
FORMULA
Empirical: a(n) = 3*a(n-1) + 26*a(n-2) + 16*a(n-3) - 99*a(n-4) + 2*a(n-5) + 81*a(n-6) - 330*a(n-7) + 340*a(n-8) - 212*a(n-9) + 124*a(n-10) + 81*a(n-11) - 30*a(n-12) + 5*a(n-13) - 3*a(n-14) - a(n-15).
Empirical formula verified: see link. - Robert Israel, Oct 06 2019
EXAMPLE
Some solutions for n=5:
0 0 3 0 0 0 0 0 0 3 0 0 0 0 3 0 0 0 0 0
3 0 0 3 0 0 0 3 0 0 0 0 0 0 0 3 0 3 3 0
0 3 1 0 3 0 1 0 0 3 0 3 0 3 1 0 0 0 0 3
0 0 0 3 0 0 3 0 0 3 0 0 3 0 0 3 1 3 0 0
0 3 0 0 0 3 0 0 0 0 0 0 0 0 3 0 0 0 0 0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2011
STATUS
approved