A221572 Number of 0..7 arrays of length n with each element differing from at least one neighbor by something other than 1

0, 50, 314, 2500, 19014, 145800, 1116400, 8550512, 65485386, 501533796, 3841097940, 29417832750, 225302467392, 1725524876860, 13215284016064, 101211946587176, 775152325067630, 5936662096954472, 45467136862793520

Offset

1,2

Comments

Column 7 of A221573

Links

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

Formula

Empirical: a(n) = 7*a(n-1) +4*a(n-2) +5*a(n-3) +20*a(n-4) +20*a(n-5) +23*a(n-6) -6*a(n-7) +3*a(n-8).

Empirical g.f.: -2*x^2*(25-18*x+51*x^2+4*x^3+66*x^4-18*x^5+6*x^6) / ( -1+7*x+4*x^2+5*x^3+20*x^4+20*x^5+23*x^6-6*x^7+3*x^8 ). - R. J. Mathar, Jun 06 2013

Example

Some solutions for n=6
..6....5....1....2....1....3....6....4....4....2....7....0....1....2....2....6
..4....2....6....7....6....6....0....2....0....7....4....4....6....6....4....2
..6....4....7....0....0....1....2....2....7....0....2....1....3....2....1....4
..2....5....4....3....0....4....0....6....4....0....7....1....2....3....6....0
..6....7....3....3....0....7....7....1....0....1....5....6....5....0....6....1
..1....7....1....0....5....0....4....1....0....1....3....0....3....0....0....4

Crossrefs

Sequence in context: A205620 A183698 A183690 * A124809 A261803 A184564

Adjacent sequences: A221569 A221570 A221571 * A221573 A221574 A221575

Keyword

nonn

Author

R. H. Hardin Jan 20 2013

Status

approved