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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 53 |
| 5 | 177 |
| 6 | 828 |
| 7 | 3094 |
| 8 | 14824 |
| 9 | 58033 |
| 10 | 281684 |
| 11 | 1141169 |
| 12 | 5586654 |
| 13 | 23180041 |
| 14 | 114064351 |
| 15 | 481510517 |
| 16 | 2378380394 |
| 17 | 10178922398 |
| 18 | 50407914795 |
| 19 | 218056976919 |
| 20 | 1081961659417 |
| 21 | 4722055959715 |
| 22 | 23463965963873 |
| 23 | 103158013453456 |
| 24 | 513166328831217 |
| 25 | 2270192767159448 |
| 26 | 11303062638778405 |
| 27 | 50271038033668035 |
[1,1,4,12,53,177,828,3094,14824,58033,281684, 1141169,5586654,23180041,114064351,481510517, 2378380394,10178922398,50407914795,218056976919, 1081961659417,4722055959715,23463965963873, 103158013453456,513166328831217,2270192767159448, 11303062638778405,50271038033668035] |