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A064815
Related to enumeration of finite automata.
1
1, 1, 6, 60, 900, 17880, 441960, 13064400, 449386800, 17630743200, 776922300000, 37990482532800, 2041238825908800, 119537563260528000, 7577709770318352000, 516967507671286560000, 37765578642439804128000
OFFSET
1,3
LINKS
M. Domaratzki, Improved bounds on the number of automata accepting finite languages, in Computing and Combinatorics Conference: COCOON'02.
M. Domaratzki, Improved bounds on the number of automata accepting finite languages, Internat. J. Found. Comput. Sci. 15 (2004), 143-161.
FORMULA
a(n) = 2*(2n-3)*a(n-1) + 2*(2n-5)*(n-4)*a(n-2) for n >= 4; a(n) = A000407(n-2) for n <= 3.
PROG
(PARI) { for (n=1, 100, if (n>3, a=2*(2*n-3)*a1 + 2*(2*n-5)*(n-4)*a2; a2=a1; a1=a, if (n>2, a=a1=6, a=a2=1)); write("b064815.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 27 2009
CROSSREFS
Cf. A000407.
Sequence in context: A177191 A010040 A138379 * A331120 A368505 A296956
KEYWORD
easy,nonn
AUTHOR
Mike Domaratzki (mdomaratzki(AT)alumni.uwaterloo.ca), Oct 22 2001
EXTENSIONS
a(16)-a(17) from Harry J. Smith, Sep 27 2009
STATUS
approved