A261603 Number of permutations of the set {1,2,...,n}^2 such that first coordinates of first floor(n^2/2) elements are nondecreasing and second coordinates of the remaining ceiling(n^2/2) elements are nondecreasing.
1, 10, 1944, 15858432, 7763310604800, 338060641751949312000, 1761952269949978269865476096000, 1455735772788406631491292993098686136320000, 241478064611792629237655079290406479536142910750720000000, 10017186663047806334488985920024892176911305625097432121928056832000000000
Offset: 1
Keywords
Crossrefs
Main diagonal of A261602.
Extensions
a(7)-a(10) from Max Alekseyev, Jul 13 2022