A064049 Number of possible arrangements of numbers 1 to n*(n+1)/2 in a triangle of n rows so that each row and each diagonal is increasing or decreasing.

1, 6, 24, 180, 4212, 461064, 302693712, 1383863258256, 49604541999616656, 15532699074331383195984, 46930820867492201530663876176, 1498790780922460190338294851221480784, 550147065342809949572433566527924149475155792, 2507733133290710762054763613438903427360533018661706960

Offset: 1

Author

Floor van Lamoen, Aug 24 2001

Keywords

• nonn

Examples

			The following triangle of 4 rows satisfies the requirements:
....1
...3 2
..4 5 8
.6 7 9 10
		

Links

• Max Alekseyev, Table of n, a(n) for n = 1..18

Crossrefs

a(n)=6*A064050(n) for n>1.

Extensions

a(7) from Lars Blomberg, Apr 11 2012

Terms a(8) onward from Max Alekseyev, Jul 20 2024