|
%I #23 Dec 01 2018 08:02:56
%S 2,8,60,560,6300,83160,1261260,21621600,413513100,8729721000,
%T 201656555100,5059746291600,137034795397500,3984550204635000,
%U 123805667072587500,4093840724533560000,143540290403957947500,5319434291440794525000,207753461493493252837500,8528826313943407221750000
%N a(1)=2, a(n) = (4n/3)*(2n-1)!! (see A001147) for n>1.
%H Bela Bollobas, <a href="https://doi.org/10.1016/0095-8956(78)90011-4">The number of 1-factors in 2k-connected graphs</a>, J. Combin. Theory Ser. B 25 (1978), no. 3, 363--366. MR0516268 (80m:05060). See Eq. (2).
%F (n-1)*a(n) =n*(2n-1)*a(n-1), n>2. - _R. J. Mathar_, Mar 27 2012
%t a[n_] := If[n == 1, 2, (4n/3)*(2n - 1)!!]; Array[a, 20] (* _Amiram Eldar_, Dec 01 2018 *)
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Mar 27 2012
|
