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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 117 |
| 6 | 706 |
| 7 | 4962 |
| 8 | 39817 |
| 9 | 359171 |
| 10 | 3597936 |
| 11 | 39630372 |
| 12 | 476066277 |
| 13 | 6194080387 |
| 14 | 86776390796 |
| 15 | 1302376048620 |
| 16 | 20847721870931 |
| 17 | 354549730559949 |
| 18 | 6384006047649910 |
| 19 | 121330369923079290 |
| 20 | 2427196999663678987 |
| 21 | 50981866833670160201 |
| 22 | 1121806937829102793662 |
[1,1,2,6,23,117,706,4962,39817,359171,3597936, 39630372,476066277,6194080387,86776390796, 1302376048620,20847721870931,354549730559949, 6384006047649910,121330369923079290, 2427196999663678987,50981866833670160201, 1121806937829102793662] |