A205208 Number of (n+1) X 2 0..2 arrays with the determinants of 2 X 2 subblocks nondecreasing rightwards and downwards.

81, 452, 1970, 8128, 33386, 139390, 588254, 2496440, 10620486, 45235186, 192770330, 821702110, 3502996038, 14934443890, 63672178746, 271466142110, 1157401680934, 4934619974706, 21038940313818, 89700376749918

Offset

1,1

Comments

Column 1 of A205215.

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 11*a(n-2) - 9*a(n-3) + 30*a(n-4) - 16*a(n-5) for n>13.

Empirical g.f.: x*(81 - 115*x - 303*x^2 + 39*x^3 - 202*x^4 + 562*x^5 + 1054*x^6 + 106*x^7 - 822*x^8 - 614*x^9 - 46*x^10 + 84*x^11 + 32*x^12) / ((1 - x)*(1 - 2*x)*(1 - 4*x - 3*x^2 + 8*x^3)). - Colin Barker, Mar 03 2018

Example

Some solutions for n=4:
  1 2   0 0   1 0   2 1   1 0   1 0   1 2   2 2   2 0   2 1
  0 0   2 1   2 0   0 0   1 0   0 0   2 2   0 0   2 0   1 0
  0 1   0 0   1 0   1 0   1 1   0 0   1 0   0 1   1 0   1 0
  0 1   2 2   0 0   1 1   1 2   1 1   1 0   0 0   1 1   2 0
  0 0   0 1   2 1   0 1   0 2   1 1   1 2   0 2   0 1   2 2

Crossrefs

Cf. A205215.

Sequence in context: A205215 A206223 A236669 * A236664 A253533 A183971

Adjacent sequences: A205205 A205206 A205207 * A205209 A205210 A205211

Keyword

nonn

Author

R. H. Hardin, Jan 23 2012

Status

approved