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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 12 |
| 5 | 38 |
| 6 | 143 |
| 7 | 490 |
| 8 | 1768 |
| 9 | 6268 |
| 10 | 22610 |
| 11 | 81620 |
| 12 | 297160 |
| 13 | 1086172 |
| 14 | 3991995 |
| 15 | 14731290 |
| 16 | 54587280 |
| 17 | 202992808 |
| 18 | 757398510 |
| 19 | 2834493948 |
| 20 | 10637507400 |
| 21 | 40023577524 |
| 22 | 150946230006 |
| 23 | 570534370692 |
| 24 | 2160865067312 |
| 25 | 8199710635816 |
[0,1,2,12,38,143,490,1768,6268,22610,81620,297160, 1086172,3991995,14731290,54587280,202992808, 757398510,2834493948,10637507400,40023577524, 150946230006,570534370692,2160865067312, 8199710635816] |