A258736 Number of length n+6 0..3 arrays with at most one downstep in every n consecutive neighbor pairs.
16384, 43681, 68120, 98676, 149960, 228081, 331584, 465580, 635992, 849708, 1114752, 1440474, 1837760, 2319263, 2899656, 3595908, 4427584, 5417170, 6590424, 7976754, 9609624, 11526989, 13771760, 16392300, 19442952, 22984600, 27085264
Offset: 1
Keywords
Examples
Some solutions for n=4: ..2....1....1....2....0....0....2....1....3....0....2....1....0....3....0....0 ..2....0....1....0....0....0....0....1....3....1....1....1....2....3....0....0 ..0....1....2....0....2....2....0....0....2....0....1....2....3....0....2....3 ..0....1....0....0....2....2....0....1....2....0....3....0....3....0....2....0 ..2....1....0....0....2....0....0....2....2....3....3....2....1....0....0....0 ..2....2....0....1....2....0....2....2....2....3....1....2....1....0....0....1 ..3....3....2....2....2....0....0....3....0....0....1....2....1....1....0....3 ..1....3....1....2....0....0....1....3....2....0....1....0....2....3....1....3 ..3....3....1....3....2....1....2....1....2....3....3....0....3....1....2....0 ..3....2....1....0....3....0....2....1....3....3....1....0....2....1....3....0
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A258730.
Formula
Empirical: a(n) = (1/5040)*n^7 + (1/72)*n^6 + (149/360)*n^5 + (239/36)*n^4 + (297247/720)*n^3 + (187297/72)*n^2 + (178036/35)*n + 2212 for n>4.
Empirical g.f.: x*(16384 - 87391*x + 177424*x^2 - 140720*x^3 - 31344*x^4 + 116775*x^5 - 39024*x^6 - 13988*x^7 - 31192*x^8 + 58867*x^9 - 31680*x^10 + 5890*x^11) / (1 - x)^8. - Colin Barker, Jan 26 2018
Comments