A064815 - OEIS

%I #10 Jun 19 2018 05:12:27

%S 1,1,6,60,900,17880,441960,13064400,449386800,17630743200,

%T 776922300000,37990482532800,2041238825908800,119537563260528000,

%U 7577709770318352000,516967507671286560000,37765578642439804128000

%N Related to enumeration of finite automata.

%H Harry J. Smith, <a href="/A064815/b064815.txt">Table of n, a(n) for n = 1..100</a>

%H M. Domaratzki, <a href="https://doi.org/10.1007/3-540-45005-X_18">Improved bounds on the number of automata accepting finite languages</a>, in Computing and Combinatorics Conference: COCOON'02.

%H M. Domaratzki, <a href="https://doi.org/10.1142/S0129054104002352">Improved bounds on the number of automata accepting finite languages</a>, Internat. J. Found. Comput. Sci. 15 (2004), 143-161.

%F 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.

%o (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

%Y Cf. A000407.

%K easy,nonn

%O 1,3

%A Mike Domaratzki (mdomaratzki(AT)alumni.uwaterloo.ca), Oct 22 2001

%E a(16)-a(17) from _Harry J. Smith_, Sep 27 2009