1,2

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.

Cf. A097871.

Sequence in context: A139189 A002008 A099123 this_sequence A054752 A128275 A028448

Adjacent sequences: A097990 A097991 A097992 this_sequence A097994 A097995 A097996

nonn

Guenter Stertenbrink (Sterten(AT)aol.com), Sep 08 2004