n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 20 |
3 | 116 |
4 | 736 |
5 | 4952 |
6 | 34716 |
7 | 250868 |
8 | 1855520 |
9 | 13979192 |
10 | 106901032 |
11 | 827644424 |
12 | 6474611984 |
13 | 51100656544 |
14 | 406400018092 |
15 | 3253636464756 |
16 | 26201323746880 |
17 | 212093247874904 |
18 | 1724793778005528 |
19 | 14084738953391768 |
20 | 115447965121881856 |
[1,4,20,116,736,4952,34716,250868,1855520, 13979192,106901032,827644424,6474611984, 51100656544,406400018092,3253636464756, 26201323746880,212093247874904,1724793778005528, 14084738953391768,115447965121881856] |