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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 44 |
| 5 | 155 |
| 6 | 615 |
| 7 | 2411 |
| 8 | 9970 |
| 9 | 40891 |
| 10 | 174401 |
| 11 | 740721 |
| 12 | 3229916 |
| 13 | 14042215 |
| 14 | 62258717 |
| 15 | 275471949 |
| 16 | 1237417112 |
| 17 | 5550593831 |
| 18 | 25195430116 |
| 19 | 114255398662 |
| 20 | 523102262154 |
| 21 | 2393378795877 |
| 22 | 11036621432426 |
| 23 | 50872385276570 |
| 24 | 236019676201247 |
| 25 | 1094752434489828 |
| 26 | 5105652630068450 |
| 27 | 23809462275320561 |
[1,1,4,12,44,155,615,2411,9970,40891,174401, 740721,3229916,14042215,62258717,275471949, 1237417112,5550593831,25195430116,114255398662, 523102262154,2393378795877,11036621432426, 50872385276570,236019676201247,1094752434489828, 5105652630068450,23809462275320561] |