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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 116 |
| 5 | 600 |
| 6 | 3072 |
| 7 | 15634 |
| 8 | 79256 |
| 9 | 400718 |
| 10 | 2022160 |
| 11 | 10189974 |
| 12 | 51292608 |
| 13 | 257965512 |
| 14 | 1296483996 |
| 15 | 6512176890 |
| 16 | 32694946020 |
| 17 | 164082802440 |
| 18 | 823188507360 |
| 19 | 4128668625430 |
| 20 | 20701989426800 |
| 21 | 103781348220380 |
| 22 | 520167491584660 |
| 23 | 2606714240022090 |
| 24 | 13061050758478620 |
| 25 | 65434115386531850 |
[0,1,4,22,116,600,3072,15634,79256,400718,2022160, 10189974,51292608,257965512,1296483996,6512176890, 32694946020,164082802440,823188507360, 4128668625430,20701989426800,103781348220380, 520167491584660,2606714240022090, 13061050758478620,65434115386531850] |