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A194721
Number of n-ary words beginning with the first character of the alphabet, that can be built by inserting nine doublets into the initially empty word.
2
0, 1, 24310, 2699837, 52955950, 464221105, 2561439806, 10466643805, 34648845862, 98156060225, 246643289830, 563506356061, 1191627482750, 2363434581937, 4441172224750, 7969478316605, 13742556531766, 22888430598145, 36972962559062, 58126513174525, 89196318660430
OFFSET
0,3
LINKS
FORMULA
G.f.: -x * (1 +24301*x +2481083*x^2 +29532493*x^3 +82769773*x^4 +66140687*x^5 +14462017*x^6 +624055*x^7 +1430*x^8) / (x-1)^9.
a(0) = 0, a(n) = 1 +(16 +(119 +(544 +(1700 +(3808 +(6188 +(7072 +4862 * (n-1)) *(n-1)) *(n-1)) *(n-1)) *(n-1)) *(n-1)) *(n-1)) *(n-1) for n>0.
EXAMPLE
a(1) = 1: a^18 (with 1-ary alphabet {a}).
MAPLE
a:= n-> `if`(n=0, 0, (x-> 1+(16+(119+(544+(1700+(3808+(6188+(7072+4862
*x)*x)*x)*x)*x)*x)*x)*x)(n-1)):
seq(a(n), n=0..30);
CROSSREFS
Row n=9 of A183134.
Sequence in context: A078870 A154069 A318630 * A140923 A208622 A294856
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 02 2011
STATUS
approved