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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 56 |
| 4 | 661 |
| 5 | 9141 |
| 6 | 142522 |
| 7 | 2448544 |
| 8 | 45653707 |
| 9 | 913964706 |
| 10 | 19491269046 |
| 11 | 440154262428 |
| 12 | 10475920613965 |
| 13 | 261802864005533 |
| 14 | 6848792691398646 |
| 15 | 187061918111607286 |
| 16 | 5322557388634585229 |
| 17 | 157460119081722965460 |
| 18 | 4834825995463338092669 |
| 19 | 153840302781842431823086 |
[1,1,6,56,661,9141,142522,2448544,45653707, 913964706,19491269046,440154262428,10475920613965, 261802864005533,6848792691398646, 187061918111607286,5322557388634585229, 157460119081722965460,4834825995463338092669, 153840302781842431823086] |