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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 53 |
| 5 | 250 |
| 6 | 1234 |
| 7 | 6295 |
| 8 | 32925 |
| 9 | 175616 |
| 10 | 951596 |
| 11 | 5223658 |
| 12 | 28987546 |
| 13 | 162349759 |
| 14 | 916502869 |
| 15 | 5209630108 |
| 16 | 29792226533 |
| 17 | 171284524184 |
| 18 | 989460348216 |
| 19 | 5740230703588 |
| 20 | 33429379234924 |
| 21 | 195361236443008 |
| 22 | 1145312096390408 |
| 23 | 6733896357727242 |
| 24 | 39697441350016170 |
| 25 | 234596104853541967 |
[1,1,3,12,53,250,1234,6295,32925,175616,951596, 5223658,28987546,162349759,916502869,5209630108, 29792226533,171284524184,989460348216, 5740230703588,33429379234924,195361236443008, 1145312096390408,6733896357727242, 39697441350016170,234596104853541967] |