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| n | a(n) |
|---|---|
| 1 | 15 |
| 2 | 225 |
| 3 | 1071 |
| 4 | 4089 |
| 5 | 13865 |
| 6 | 39831 |
| 7 | 110775 |
| 8 | 289467 |
| 9 | 730377 |
| 10 | 1811997 |
| 11 | 4393069 |
| 12 | 10558951 |
| 13 | 25146429 |
| 14 | 59475625 |
| 15 | 140190519 |
| 16 | 329138641 |
| 17 | 771108603 |
| 18 | 1803405621 |
| 19 | 4211351857 |
| 20 | 9825749755 |
| 21 | 22905455175 |
| 22 | 53364801587 |
| 23 | 124272402673 |
| 24 | 289284276825 |
[15,225,1071,4089,13865,39831,110775,289467, 730377,1811997,4393069,10558951,25146429,59475625, 140190519,329138641,771108603,1803405621, 4211351857,9825749755,22905455175,53364801587, 124272402673,289284276825] |