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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 68 |
| 5 | 255 |
| 6 | 989 |
| 7 | 3955 |
| 8 | 16147 |
| 9 | 67057 |
| 10 | 282495 |
| 11 | 1203909 |
| 12 | 5180147 |
| 13 | 22480686 |
| 14 | 98268169 |
| 15 | 432231388 |
| 16 | 1911944862 |
| 17 | 8499084865 |
| 18 | 37945861008 |
| 19 | 170096408313 |
| 20 | 765203667592 |
| 21 | 3453498192794 |
| 22 | 15632819897677 |
| 23 | 70956387986424 |
| 24 | 322865559744975 |
| 25 | 1472499460157086 |
| 26 | 6729929928075598 |
| 27 | 30818993591307189 |
[1,2,6,19,68,255,989,3955,16147,67057,282495, 1203909,5180147,22480686,98268169,432231388, 1911944862,8499084865,37945861008,170096408313, 765203667592,3453498192794,15632819897677, 70956387986424,322865559744975,1472499460157086, 6729929928075598,30818993591307189] |