%I #13 Nov 26 2018 04:06:46

%S -1,-1,0,1,4,8,18,33,68,124,250,460,922,1714,3430,6433,12868,24308,

%T 48618,92376,184754,352714,705430,1352076,2704154,5200298,10400598,

%U 20058298,40116598,77558758,155117518,300540193,601080388,1166803108,2333606218,4537567648,9075135298,17672631898,35345263798,68923264408,137846528818

%N a(n) = binomial(n, [n/2]) - 2.

%H J.-L. Baril, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v18i1p178">Classical sequences revisited with permutations avoiding dotted pattern</a>, Electronic Journal of Combinatorics, 18 (2011), #P178. See Table 3.

%F Conjecture: +(n+1)*a(n) +2*(-n-1)*a(n-1) +(-3*n+7)*a(n-2) +2*(4*n-9)*a(n-3) +4*(-n+3)*a(n-4)=0. - _R. J. Mathar_, Jul 17 2014

%t Table[Binomial[n,Floor[n/2]]-2,{n,0,40}] (* _Harvey P. Dale_, Apr 12 2018 *)

%Y Cf. A001405.

%K sign

%O 0,5

%A _N. J. A. Sloane_, Dec 03 2011