A064815 Related to enumeration of finite automata.

1, 1, 6, 60, 900, 17880, 441960, 13064400, 449386800, 17630743200, 776922300000, 37990482532800, 2041238825908800, 119537563260528000, 7577709770318352000, 516967507671286560000, 37765578642439804128000

Offset

1,3

Links

Harry J. Smith, Table of n, a(n) for n = 1..100

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

Adjacent sequences: A064812 A064813 A064814 * A064816 A064817 A064818

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