A202974 Number of n X 3 0..1 arrays with every nonzero element less than or equal to at least two horizontal and vertical neighbors.

1, 4, 17, 58, 215, 866, 3507, 14120, 56921, 229860, 928443, 3749720, 15144167, 61165438, 247041429, 997775144, 4029911351, 16276407572, 65738788527, 265512410122, 1072378133103, 4331228325504, 17493399301365, 70654095337584

Offset

1,2

Comments

Column 3 of A202979.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 16*a(n-3) - 14*a(n-4) - 3*a(n-5) + 8*a(n-6) - 9*a(n-7) - 2*a(n-8) + 6*a(n-9) + 2*a(n-10).

Empirical g.f.: x*(1 - 2*x + 4*x^2 - 16*x^3 + 4*x^4 + x^5 - 10*x^6 + 4*x^7 + 8*x^8 + 2*x^9) / (1 - 6*x + 11*x^2 - 16*x^3 + 14*x^4 + 3*x^5 - 8*x^6 + 9*x^7 + 2*x^8 - 6*x^9 - 2*x^10). - Colin Barker, Jun 03 2018

Example

Some solutions for n=5:
  1 1 1    0 1 1    1 1 1    0 1 1    0 0 0    1 1 1    1 1 0
  1 1 1    1 1 1    1 1 1    1 1 1    0 1 1    1 0 1    1 1 1
  0 0 0    1 1 1    1 0 0    1 0 1    1 1 1    1 0 1    1 0 1
  0 0 0    1 1 0    1 1 1    1 1 1    1 1 1    1 0 1    1 1 1
  0 0 0    0 0 0    1 1 1    0 1 1    0 1 1    1 1 1    0 0 0

Crossrefs

Cf. A202979.

Sequence in context: A255271 A293798 A027075 * A034331 A107278 A006762

Adjacent sequences: A202971 A202972 A202973 * A202975 A202976 A202977

Keyword

nonn

Author

R. H. Hardin, Dec 26 2011

Status

approved