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A239368 Number of words of length n over the alphabet {0,...,n-1} that avoid the pattern 1111. 2
1, 1, 4, 27, 252, 3020, 44220, 765030, 15269520, 345376080, 8730489600, 243911883600, 7463164262400, 248207881521600, 8915064168410400, 343923449355486000, 14182674669779616000, 622591172035376544000, 28986699477880400256000, 1426677017904959524704000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..350

FORMULA

Recursion: see Maple program.

MAPLE

a:= proc(n) option remember; `if`(n<3, n^n,

     ((105*n^3-252*n^2+175*n-36) *a(n-1) -2*(n-1)^2 *a(n-2)

     +2*(5*n-2)*(n-1)^2*(n-2)^2*a(n-3)) / (4*(2*n-1)*(5*n-7)))

    end:

seq(a(n), n=0..20);  # Alois P. Heinz, Jul 20 2014

CROSSREFS

Cf. A012244, A239295.

Sequence in context: A239377 A239371 A201996 * A245408 A243696 A158836

Adjacent sequences:  A239365 A239366 A239367 * A239369 A239370 A239371

KEYWORD

nonn

AUTHOR

Chad Brewbaker, Mar 17 2014

EXTENSIONS

a(8)-a(11) from Alois P. Heinz, Mar 17 2014

a(12)-a(19) from Alois P. Heinz, Jul 20 2014

STATUS

approved

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Last modified October 22 09:51 EDT 2021. Contains 348160 sequences. (Running on oeis4.)