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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 15 |
| 3 | 80 |
| 4 | 396 |
| 5 | 1788 |
| 6 | 7831 |
| 7 | 33170 |
| 8 | 137868 |
| 9 | 563486 |
| 10 | 2275119 |
| 11 | 9091772 |
| 12 | 36031648 |
| 13 | 141793168 |
| 14 | 554669335 |
| 15 | 2158604934 |
| 16 | 8363066408 |
| 17 | 32273565050 |
| 18 | 124112115647 |
| 19 | 475807505288 |
| 20 | 1819019281732 |
| 21 | 6936664653476 |
| 22 | 26392068734023 |
| 23 | 100206016839642 |
[2,15,80,396,1788,7831,33170,137868,563486, 2275119,9091772,36031648,141793168,554669335, 2158604934,8363066408,32273565050,124112115647, 475807505288,1819019281732,6936664653476, 26392068734023,100206016839642] |