

A255627


Number of length n+5 0..2 arrays with at most two downsteps in every n consecutive neighbor pairs.


1



729, 2187, 6561, 17622, 40659, 83325, 156563, 275166, 458604, 731981, 1127139, 1683927, 2451654, 3490746, 4874628, 6691853, 9048501, 12070872, 15908498, 20737500, 26764317, 34229835, 43413945, 54640560, 68283122, 84770631
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OFFSET

1,1


COMMENTS

Row 5 of A255622.


LINKS

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


FORMULA

Empirical: a(n) = (1/40320)*n^8 + (19/10080)*n^7 + (31/576)*n^6 + (122/45)*n^5 + (188527/5760)*n^4 + (32263/1440)*n^3 + (276001/672)*n^2  (152493/280)*n + 387 for n>3.
Empirical g.f.: x*(729  4374*x + 13122*x^2  23931*x^3 + 26403*x^4  15630*x^5 + 2474*x^6 + 1593*x^7 + 693*x^8  1849*x^9 + 924*x^10  153*x^11) / (1  x)^9.  Colin Barker, Jan 20 2018


EXAMPLE

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


CROSSREFS

Cf. A255622.
Sequence in context: A267697 A232925 A255112 * A139308 A295024 A167728
Adjacent sequences: A255624 A255625 A255626 * A255628 A255629 A255630


KEYWORD

nonn


AUTHOR

R. H. Hardin, Feb 28 2015


STATUS

approved



