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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 21 |
| 3 | 159 |
| 4 | 1257 |
| 5 | 10046 |
| 6 | 81811 |
| 7 | 674184 |
| 8 | 5605141 |
| 9 | 46920874 |
| 10 | 394949193 |
| 11 | 3339464105 |
| 12 | 28343082002 |
| 13 | 241324470723 |
| 14 | 2060357315568 |
| 15 | 17632454524499 |
| 16 | 151211115930880 |
| 17 | 1299121121946684 |
| 18 | 11179500360964780 |
| 19 | 96344672766997340 |
| 20 | 831385476662968094 |
| 21 | 7182777882757416692 |
[1,3,21,159,1257,10046,81811,674184,5605141, 46920874,394949193,3339464105,28343082002, 241324470723,2060357315568,17632454524499, 151211115930880,1299121121946684, 11179500360964780,96344672766997340, 831385476662968094,7182777882757416692] |