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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 30 |
| 3 | 138 |
| 4 | 606 |
| 5 | 2610 |
| 6 | 11070 |
| 7 | 46386 |
| 8 | 192606 |
| 9 | 793938 |
| 10 | 3253038 |
| 11 | 13261746 |
| 12 | 53832462 |
| 13 | 217707762 |
| 14 | 877594086 |
| 15 | 3527521794 |
| 16 | 14142930774 |
| 17 | 56574143754 |
| 18 | 225841103190 |
| 19 | 899866007610 |
| 20 | 3579435531846 |
| 21 | 14215941861138 |
| 22 | 56378805654510 |
| 23 | 223297285830858 |
| 24 | 883326046736814 |
[1,6,30,138,606,2610,11070,46386,192606,793938, 3253038,13261746,53832462,217707762,877594086, 3527521794,14142930774,56574143754,225841103190, 899866007610,3579435531846,14215941861138, 56378805654510,223297285830858,883326046736814] |