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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 77 |
| 5 | 389 |
| 6 | 2128 |
| 7 | 12019 |
| 8 | 70185 |
| 9 | 418788 |
| 10 | 2544938 |
| 11 | 15687842 |
| 12 | 97871618 |
| 13 | 616729500 |
| 14 | 3919686231 |
| 15 | 25096525793 |
| 16 | 161723865118 |
| 17 | 1048085548563 |
| 18 | 6826585371618 |
| 19 | 44664343473618 |
| 20 | 293407529533947 |
| 21 | 1934484748893113 |
| 22 | 12796683165889635 |
| 23 | 84906535878961845 |
[1,1,4,16,77,389,2128,12019,70185,418788,2544938, 15687842,97871618,616729500,3919686231, 25096525793,161723865118,1048085548563, 6826585371618,44664343473618,293407529533947, 1934484748893113,12796683165889635, 84906535878961845] |