A255113 Number of length n+6 0..2 arrays with at most one downstep in every n consecutive neighbor pairs.
2187, 5157, 7498, 10125, 14001, 19263, 25578, 33063, 41851, 52092, 63954, 77624, 93309, 111237, 131658, 154845, 181095, 210730, 244098, 281574, 323561, 370491, 422826, 481059, 545715, 617352, 696562, 783972, 880245, 986081, 1102218, 1229433
Offset: 1
Keywords
Examples
Some solutions for n=4: ..1....0....1....0....1....2....1....0....2....0....1....1....2....2....0....0 ..2....2....2....2....1....0....1....2....1....0....2....1....2....1....1....2 ..2....0....0....1....1....0....2....2....1....2....2....2....0....1....2....0 ..1....0....0....1....1....1....1....1....1....0....2....0....1....2....2....2 ..1....0....0....2....1....1....1....1....1....0....0....1....1....2....2....2 ..2....0....1....2....2....2....1....2....1....0....0....1....1....2....0....2 ..2....0....1....2....1....2....1....2....1....2....0....2....1....2....1....0 ..0....2....2....0....2....2....2....1....2....2....2....2....0....0....1....0 ..2....1....2....0....2....0....0....1....1....0....0....2....0....1....1....0 ..2....2....1....2....2....1....1....2....1....1....0....0....0....2....0....2
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A255107.
Formula
Empirical: a(n) = (1/120)*n^5 + (3/8)*n^4 + (149/24)*n^3 + (2521/8)*n^2 + (56417/60)*n + 385 for n>4.
Empirical g.f.: x*(2187 - 7965*x + 9361*x^2 - 1248*x^3 - 4614*x^4 + 1405*x^5 + 1230*x^6 + 564*x^7 - 1354*x^8 + 435*x^9) / (1 - x)^6. - Colin Barker, Jan 24 2018
Comments