OFFSET
1,3
COMMENTS
Appears to be the number of tilings of a 7 X 2n rectangle with 7 X 1 heptominoes. - M. Poyraz Torcuk, Dec 25 2021
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-4) + a(n-7).
Empirical g.f.: x*(1 + 2*x^2 + 2*x^3 + x^5 + x^6) / (1 - x - 2*x^4 - x^7). - Colin Barker, Feb 23 2019
EXAMPLE
Some solutions for n=7:
0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0
0 1 1 1 0 0 0 0 0 1 1 0 0 0 0 0 1 1 1 0
0 1 1 0 0 0 0 0 1 1 1 0 0 0 0 0 1 1 0 0
0 0 0 0 0 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0
0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 15 2017
STATUS
approved