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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 36 |
| 5 | 190 |
| 6 | 980 |
| 7 | 5705 |
| 8 | 33040 |
| 9 | 204876 |
| 10 | 1268568 |
| 11 | 8209278 |
| 12 | 53105976 |
| 13 | 354331692 |
| 14 | 2364239592 |
| 15 | 16140234825 |
| 16 | 110206067400 |
| 17 | 765868074400 |
| 18 | 5323547715200 |
| 19 | 37525317999884 |
| 20 | 264576141331216 |
| 21 | 1886768082651816 |
| 22 | 13458185494436592 |
| 23 | 96906387191038334 |
| 24 | 697931136204820336 |
[1,1,2,9,36,190,980,5705,33040,204876,1268568, 8209278,53105976,354331692,2364239592,16140234825, 110206067400,765868074400,5323547715200, 37525317999884,264576141331216,1886768082651816, 13458185494436592,96906387191038334, 697931136204820336] |