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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 115 |
| 6 | 690 |
| 7 | 4830 |
| 8 | 38641 |
| 9 | 347769 |
| 10 | 3477690 |
| 11 | 38254590 |
| 12 | 459055079 |
| 13 | 5967716027 |
| 14 | 83548024378 |
| 15 | 1253220365670 |
| 16 | 20051525850721 |
| 17 | 340875939462257 |
| 18 | 6135766910320626 |
| 19 | 116579571296091894 |
| 20 | 2331591425921837879 |
| 21 | 48963419944358595459 |
| 22 | 1077195238775889100098 |
[1,1,2,6,23,115,690,4830,38641,347769,3477690, 38254590,459055079,5967716027,83548024378, 1253220365670,20051525850721,340875939462257, 6135766910320626,116579571296091894, 2331591425921837879,48963419944358595459, 1077195238775889100098] |