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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 11 |
| 5 | 41 |
| 6 | 154 |
| 7 | 904 |
| 8 | 4927 |
| 9 | 35398 |
| 10 | 234454 |
| 11 | 1965976 |
| 12 | 16589885 |
| 13 | 157974740 |
| 14 | 1480736877 |
| 15 | 16406078770 |
| 16 | 177232251249 |
| 17 | 2151696598160 |
| 18 | 25726133391191 |
| 19 | 346746928400037 |
| 20 | 4607758596471426 |
| 21 | 67562340652906942 |
| 22 | 969200312705046531 |
| 23 | 15386051753617360150 |
[1,1,1,4,11,41,154,904,4927,35398,234454,1965976, 16589885,157974740,1480736877,16406078770, 177232251249,2151696598160,25726133391191, 346746928400037,4607758596471426, 67562340652906942,969200312705046531, 15386051753617360150] |