99216domain: NAppears in sequencesa(n) = n!*Sum_{k=0..n/2} n^(2k)/(2k)!.at n=6A046707a(n) = 81*n^2 - 9.at n=34A157909Molecular topological index of the Andrásfai graphs.at n=17A192790Number of permutations p of [n] such that the up-down signature of p has nonnegative partial sums with a maximal value <= 6.at n=9A262131