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%I #8 Mar 02 2015 16:08:46
%S 1,6,24,180,4212,461064,302693712
%N 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.
%e The following triangle of 4 rows satisfies the requirements:
%e ....1
%e ...3 2
%e ..4 5 8
%e .6 7 9 10
%Y a(n)=6*A064050(n) for n>1.
%K more,nonn
%O 1,2
%A _Floor van Lamoen_, Aug 24 2001
%E a(7) from _Lars Blomberg_, Apr 11 2012
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