In A097871, for each k, decide where the first k in row k will be and where the first k in column k will be. Suppose this partial matrix is K. Sequence gives the number of such K's.
Table of n, a(n) for n=1..6.
Sequence in context: A308363 A192639 A099123 * A172806 A054752 A258978
Adjacent sequences: A097990 A097991 A097992 * A097994 A097995 A097996
Guenter Stertenbrink (Sterten(AT)aol.com), Sep 08 2004