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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 32 |
| 5 | 181 |
| 6 | 1232 |
| 7 | 9787 |
| 8 | 88832 |
| 9 | 907081 |
| 10 | 10291712 |
| 11 | 128445967 |
| 12 | 1748805632 |
| 13 | 25794366781 |
| 14 | 409725396992 |
| 15 | 6973071372547 |
| 16 | 126585529106432 |
| 17 | 2441591202059281 |
| 18 | 49863806091395072 |
| 19 | 1074927056650469527 |
| 20 | 24392086908129247232 |
| 21 | 581176736647853024581 |
[1,1,2,7,32,181,1232,9787,88832,907081,10291712, 128445967,1748805632,25794366781,409725396992, 6973071372547,126585529106432,2441591202059281, 49863806091395072,1074927056650469527, 24392086908129247232,581176736647853024581] |