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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 12 |
| 3 | 52 |
| 4 | 168 |
| 5 | 461 |
| 6 | 1133 |
| 7 | 2612 |
| 8 | 5759 |
| 9 | 12309 |
| 10 | 25666 |
| 11 | 52509 |
| 12 | 105803 |
| 13 | 210655 |
| 14 | 415349 |
| 15 | 812461 |
| 16 | 1578752 |
| 17 | 3050921 |
| 18 | 5868562 |
| 19 | 11244267 |
| 20 | 21472441 |
| 21 | 40887802 |
| 22 | 77668032 |
| 23 | 147222550 |
| 24 | 278556477 |
| 25 | 526215993 |
| 26 | 992694708 |
| 27 | 1870443330 |
| 28 | 3520594166 |
| 29 | 6620431857 |
| 30 | 12439538938 |
[0,2,12,52,168,461,1133,2612,5759,12309,25666, 52509,105803,210655,415349,812461,1578752,3050921, 5868562,11244267,21472441,40887802,77668032, 147222550,278556477,526215993,992694708, 1870443330,3520594166,6620431857,12439538938] |