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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 69 |
| 4 | 321 |
| 5 | 1491 |
| 6 | 6927 |
| 7 | 32181 |
| 8 | 149505 |
| 9 | 694563 |
| 10 | 3226767 |
| 11 | 14990757 |
| 12 | 69643329 |
| 13 | 323545587 |
| 14 | 1503112335 |
| 15 | 6983086101 |
| 16 | 32441681409 |
| 17 | 150715983939 |
| 18 | 700188979983 |
| 19 | 3252903871749 |
| 20 | 15112182426945 |
| 21 | 70207441323027 |
| 22 | 326166312572943 |
[1,3,15,69,321,1491,6927,32181,149505,694563, 3226767,14990757,69643329,323545587,1503112335, 6983086101,32441681409,150715983939,700188979983, 3252903871749,15112182426945,70207441323027, 326166312572943] |