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A253087
as a simple table
n
a(n)
0
1
1
4
2
12
3
48
4
144
5
440
6
1816
7
6816
8
25816
9
101856
10
397944
11
1573464
12
6274560
13
25071152
14
100180872
15
400625360
[1,4,12,48,144,440,1816,6816,25816,101856,397944, 1573464,6274560,25071152,100180872,400625360]