OFFSET
1,2
COMMENTS
Every 0 is next to 0 0's, every 1 is next to 1 3's, every 2 is next to 2 2's, every 3 is next to 3 1's, every 4 is next to 4 4's.
Column 3 of A196078.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = a(n-2) +2*a(n-3) +a(n-4) +3*a(n-5) +6*a(n-6) -2*a(n-7) -7*a(n-8) -3*a(n-9) -4*a(n-10) -3*a(n-11) +a(n-12) +4*a(n-13) +a(n-14) +a(n-15) -2*a(n-17).
Empirical g.f.: x^2*(2 + x - x^2 + x^3 + 3*x^4 - 3*x^5 - 8*x^6 - 3*x^7 - 5*x^8 - 2*x^9 - x^10 + 6*x^11 + 2*x^13 - 2*x^15) / (1 - x^2 - 2*x^3 - x^4 - 3*x^5 - 6*x^6 + 2*x^7 + 7*x^8 + 3*x^9 + 4*x^10 + 3*x^11 - x^12 - 4*x^13 - x^14 - x^15 + 2*x^17). - Colin Barker, May 08 2018
EXAMPLE
All solutions for n=4:
..0..1..0
..1..3..1
..1..3..1
..0..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 27 2011
STATUS
approved