

A221460


Number of 0..n arrays of length n with each element unequal to at least one neighbor, starting with 0


2



0, 2, 9, 80, 875, 11880, 192080, 3608576, 77295141, 1860100000, 49701143855, 1460328321024, 46805373800640, 1625353003293824, 60796114850390625, 2437185999638364160, 104248664384022862523, 4739500894223556407808
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OFFSET

1,2


COMMENTS

Diagonal of A221463.


LINKS

R. H. Hardin, Table of n, a(n) for n = 1..71


FORMULA

a(n) = [x^n] 1/(1  x*Sum_{k>=1} n^k*x^k).  Ilya Gutkovskiy, Mar 21 2018


EXAMPLE

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


CROSSREFS

Cf. A221463.
Sequence in context: A346671 A194471 A215629 * A122720 A109519 A193208
Adjacent sequences: A221457 A221458 A221459 * A221461 A221462 A221463


KEYWORD

nonn


AUTHOR

R. H. Hardin Jan 17 2013


STATUS

approved



