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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 26 |
| 4 | 131 |
| 5 | 706 |
| 6 | 3932 |
| 7 | 22618 |
| 8 | 133099 |
| 9 | 797545 |
| 10 | 4850296 |
| 11 | 29859028 |
| 12 | 185712831 |
| 13 | 1165227025 |
| 14 | 7366475715 |
| 15 | 46877977451 |
| 16 | 300049605259 |
| 17 | 1930395961235 |
| 18 | 12476394685445 |
| 19 | 80968876247330 |
| 20 | 527424073700966 |
| 21 | 3447190219684125 |
| 22 | 22599794010813360 |
[1,1,6,26,131,706,3932,22618,133099,797545, 4850296,29859028,185712831,1165227025,7366475715, 46877977451,300049605259,1930395961235, 12476394685445,80968876247330,527424073700966, 3447190219684125,22599794010813360] |