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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 37 |
| 5 | 272 |
| 6 | 2637 |
| 7 | 32469 |
| 8 | 493602 |
| 9 | 9062503 |
| 10 | 197409097 |
| 11 | 5027822588 |
| 12 | 147896295785 |
| 13 | 4972353491993 |
| 14 | 189357434418082 |
| 15 | 8104194176872583 |
| 16 | 387121098095180237 |
| 17 | 20513320778472547576 |
| 18 | 1199236185075846230469 |
| 19 | 76970026071431034905229 |
| 20 | 5399593095642890354948802 |
[1,1,2,7,37,272,2637,32469,493602,9062503, 197409097,5027822588,147896295785,4972353491993, 189357434418082,8104194176872583, 387121098095180237,20513320778472547576, 1199236185075846230469,76970026071431034905229, 5399593095642890354948802] |