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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 21 |
| 3 | 152 |
| 4 | 1518 |
| 5 | 11499 |
| 6 | 98343 |
| 7 | 556989 |
| 8 | 3662106 |
| 9 | 16124119 |
| 10 | 85225430 |
| 11 | 312644461 |
| 12 | 1392323322 |
| 13 | 4440186675 |
| 14 | 17261781178 |
| 15 | 49427257741 |
| 16 | 171990299716 |
| 17 | 450949023627 |
| 18 | 1430808802178 |
| 19 | 3490735786071 |
| 20 | 10240050566337 |
| 21 | 23490703637555 |
[3,21,152,1518,11499,98343,556989,3662106, 16124119,85225430,312644461,1392323322,4440186675, 17261781178,49427257741,171990299716,450949023627, 1430808802178,3490735786071,10240050566337, 23490703637555] |