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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 4 |
| 6 | 10 |
| 7 | 19 |
| 8 | 46 |
| 9 | 199 |
| 10 | 890 |
| 11 | 4075 |
| 12 | 20900 |
| 13 | 140127 |
| 14 | 1098924 |
| 15 | 9985570 |
| 16 | 103452546 |
| 17 | 1269141243 |
| 18 | 18318539114 |
| 19 | 311054175156 |
| 20 | 6154670827141 |
[1,4,10,19,46,199,890,4075,20900,140127,1098924, 9985570,103452546,1269141243,18318539114, 311054175156,6154670827141] |