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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 8 |
| 4 | 20 |
| 5 | 52 |
| 6 | 160 |
| 7 | 492 |
| 8 | 1620 |
| 9 | 5408 |
| 10 | 18504 |
| 11 | 64132 |
| 12 | 225440 |
| 13 | 800048 |
| 14 | 2865720 |
| 15 | 10341208 |
| 16 | 37568340 |
| 17 | 137270956 |
| 18 | 504176992 |
| 19 | 1860277044 |
| 20 | 6892335720 |
| 21 | 25631327688 |
| 22 | 95640894056 |
| 23 | 357975249028 |
| 24 | 1343650267296 |
| 25 | 5056424257552 |
[1,2,4,8,20,52,160,492,1620,5408,18504,64132, 225440,800048,2865720,10341208,37568340,137270956, 504176992,1860277044,6892335720,25631327688, 95640894056,357975249028,1343650267296, 5056424257552] |