A064049 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

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

EXAMPLE

The following triangle of 4 rows satisfies the requirements:

....1

...3 2

..4 5 8

.6 7 9 10

CROSSREFS