

A256821


Number of length n+6 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.


1



128, 256, 512, 1024, 1888, 3204, 5088, 7677, 11120, 15579, 21230, 28264, 36888, 47326, 59820, 74631, 92040, 112349, 135882, 162986, 194032, 229416, 269560, 314913, 365952, 423183, 487142, 558396, 637544, 725218, 822084, 928843, 1046232
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OFFSET

1,1


COMMENTS

Row 6 of A256816.


LINKS

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


FORMULA

Empirical: a(n) = (1/120)*n^5 + (5/24)*n^4 + (111/8)*n^3  (701/24)*n^2 + (11767/60)*n  253 for n>4.
Empirical g.f.: x*(128  512*x + 896*x^2  768*x^3 + 224*x^4 + 68*x^5  24*x^6  7*x^7  14*x^8 + 10*x^9) / (1  x)^6.  Colin Barker, Jan 21 2018


EXAMPLE

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


CROSSREFS

Cf. A256816.
Sequence in context: A110290 A045028 A255997 * A172421 A235059 A045053
Adjacent sequences: A256818 A256819 A256820 * A256822 A256823 A256824


KEYWORD

nonn


AUTHOR

R. H. Hardin, Apr 10 2015


STATUS

approved



