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A194720 Number of n-ary words beginning with the first character of the alphabet, that can be built by inserting eight doublets into the initially empty word. 2
0, 1, 6435, 381333, 5068915, 33563481, 148733571, 507709165, 1443039123, 3581326065, 8006545891, 16475259141, 31690921395, 57644499913, 100028603715, 166732334301, 268424064211, 419229350625, 637511191203, 946759829365, 1376599316211, 1963918036281 (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 +6427*x +329881*x^2 +2198375*x^3 +3329195*x^4 +1251089*x^5 +91803*x^6 +429*x^7) / (x-1)^8.

a(0) = 0, a(n) = 1 +(14 +(90 +(350 +(910 +(1638 +(2002 +1430 * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1) for n>0.

EXAMPLE

a(1) = 1: a^16 (with 1-ary alphabet {a}).

MAPLE

a:= n-> `if`(n=0, 0, (x-> 1+(14+(90+(350+(910+(1638+(2002+1430*x)*

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

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

CROSSREFS

Row n=8 of A183134.

Sequence in context: A222554 A104318 A222344 * A140916 A208621 A294855

Adjacent sequences:  A194717 A194718 A194719 * A194721 A194722 A194723

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Sep 02 2011

STATUS

approved

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Last modified February 22 20:30 EST 2019. Contains 320404 sequences. (Running on oeis4.)