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

1,2

Links

Table of n, a(n) for n=1..10.

Formula

a(n) = A261602(n, floor(n^2/2)) = A261602(n, ceiling(n^2/2)).

Crossrefs

Main diagonal of A261602.

Sequence in context: A160303 A336666 A024138 * A346543 A245016 A294174

Adjacent sequences: A261600 A261601 A261602 * A261604 A261605 A261606

Keyword

nonn

Author

Max Alekseyev, Aug 25 2015

Extensions

a(7)-a(10) from Max Alekseyev, Jul 13 2022

Status

approved