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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 21 |
| 6 | 78 |
| 7 | 353 |
| 8 | 1929 |
| 9 | 12207 |
| 10 | 89402 |
| 11 | 739335 |
| 12 | 6800637 |
| 13 | 68531618 |
| 14 | 748592936 |
| 15 | 8788983173 |
| 16 | 110201690911 |
| 17 | 1468157196474 |
| 18 | 20695559603921 |
| 19 | 307590282700915 |
| 20 | 4805537369573319 |
| 21 | 78710267083015571 |
| 22 | 1348394635886684901 |
| 23 | 24109112440149231355 |
| 24 | 449050443283294835914 |
[1,1,1,2,6,21,78,353,1929,12207,89402,739335, 6800637,68531618,748592936,8788983173, 110201690911,1468157196474,20695559603921, 307590282700915,4805537369573319, 78710267083015571,1348394635886684901, 24109112440149231355,449050443283294835914] |