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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 21 |
| 5 | 50 |
| 6 | 108 |
| 7 | 364 |
| 8 | 987 |
| 9 | 1938 |
| 10 | 6150 |
| 11 | 17622 |
| 12 | 34776 |
| 13 | 121160 |
| 14 | 306852 |
| 15 | 549000 |
| 16 | 2178309 |
| 17 | 5701290 |
| 18 | 11197764 |
| 19 | 39083988 |
| 20 | 93031050 |
| 21 | 191708244 |
| 22 | 697884066 |
| 23 | 1836283246 |
| 24 | 3605645232 |
| 25 | 11442062750 |
| 26 | 32888033880 |
| 27 | 64700678454 |
[1,3,6,21,50,108,364,987,1938,6150,17622,34776, 121160,306852,549000,2178309,5701290,11197764, 39083988,93031050,191708244,697884066,1836283246, 3605645232,11442062750,32888033880,64700678454] |