A203176 Number of n X 3 0..2 arrays with every 1 immediately preceded by 0 to the left or above, no 0 immediately preceded by a 0, and every 2 immediately preceded by 0 1 to the left or above.
2, 2, 7, 17, 41, 97, 235, 607, 1415, 3486, 8648, 20838, 51170, 124939, 305270, 746199, 1820662, 4454559, 10877169, 26569604, 64944236, 158629072, 387600053, 946993492, 2313654220, 5653010591, 13810992779, 33744134975, 82444452049
Offset: 1
Keywords
Examples
Some solutions for n=5: ..0..1..2....0..1..2....0..1..0....0..1..2....0..1..2....0..1..2....0..1..0 ..1..0..1....1..0..1....1..0..1....1..0..1....1..0..1....1..0..1....1..0..1 ..2..1..0....0..1..2....0..1..0....2..1..0....0..1..0....0..1..2....2..1..2 ..0..1..1....1..0..1....1..0..1....0..2..1....1..2..1....1..0..1....0..1..0 ..1..0..2....0..1..0....0..1..0....1..0..2....2..0..1....0..1..2....1..0..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = 2*a(n-2) +10*a(n-3) +5*a(n-4) -a(n-5) -31*a(n-6) -7*a(n-7) +30*a(n-9) for n>10.
Empirical G.f.:
2*x -x^2*(2+7*x+13*x^2+7*x^3-17*x^4-50*x^5-13*x^6+18*x^7+54*x^8) / ( -1+2*x^2+10*x^3+5*x^4-x^5-31*x^6-7*x^7+30*x^9 ). - R. J. Mathar, Jul 02 2013
Comments