%I
%S 0,1,3,3,5,15,21,133,27,1215,935,12441,23673,138047,469455,
%T 1601265,9112561,18108927,182135007,161934625,3804634785,
%U 404007681,83297957567
%N Auxiliary sequence for calculation of number of even permutations of degree n and order exactly 2.
%D V. Jovovic, Some combinatorial characteristics of symmetric and alternating groups (in Russian), Belgrade, 1980, unpublished.
%F a(n) = c(n, 2), where c(n, d)=Sum_{k=1..n} (1)^(k+1)*(n1)!/(nk)! *Sum_{l:lcm{k, l}=d} c(nk, l), c(0, 1)=1.
%F a(n)=2*A048099(n)A001189(n)=A048099(n)A001465(n) a(n)=(1)^n*A001464(n)1 a(n)=a(n1)(n1)*(a(n2)+1) E.g.f.: e^x+e^(x(1/2)*x^2)  Matthew J. White (mattjameswhite(AT)hotmail.com), Mar 02 2006
%F a(n) = Sum((1)^j*n!/(2^j*j!*(n2*j)!),j=1..floor(n/2)).  _Vladeta Jovovic_, Mar 06 2006
%Y Cf. A001189, A051685.
%K sign
%O 1,3
%A _Vladeta Jovovic_
