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A194719 Number of n-ary words beginning with the first character of the alphabet, that can be built by inserting seven doublets into the initially empty word. 2
0, 1, 1716, 54573, 492724, 2467137, 8786436, 25066621, 61189668, 133071009, 264735892, 490704621, 858686676, 1432583713, 2295801444, 3554870397, 5343375556, 7826194881, 11204046708, 15718346029, 21656369652, 29356730241, 39215159236, 51690598653, 67311601764 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: -x*(1+1709*x+42582*x^2+146714*x^3+104077*x^4+13665*x^5+132*x^6) / (x-1)^7.

a(0) = 0, a(n) = 1+(12+(65+(208+(429+(572+429*(n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1) for n>0.

EXAMPLE

a(1) = 1: a^14 (with 1-ary alphabet {a}).

MAPLE

a:= n-> `if`(n=0, 0, (x-> 1+(12+(65+(208+(429+(572+429*x)*x)*x)

                          *x)*x)*x)(n-1)):

seq(a(n), n=0..30);

CROSSREFS

Row n=7 of A183134.

Sequence in context: A260474 A222343 A318628 * A140910 A208620 A294854

Adjacent sequences:  A194716 A194717 A194718 * A194720 A194721 A194722

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Sep 02 2011

STATUS

approved

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Last modified February 16 14:47 EST 2019. Contains 320163 sequences. (Running on oeis4.)