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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 68 |
| 5 | 251 |
| 6 | 983 |
| 7 | 3924 |
| 8 | 16210 |
| 9 | 67836 |
| 10 | 290213 |
| 11 | 1253258 |
| 12 | 5495220 |
| 13 | 24266747 |
| 14 | 108356043 |
| 15 | 486533258 |
| 16 | 2202981039 |
| 17 | 10019758277 |
| 18 | 45870934468 |
| 19 | 210776167079 |
| 20 | 973568507191 |
| 21 | 4510808438116 |
| 22 | 20988565551476 |
| 23 | 97915598003963 |
| 24 | 458399875204517 |
| 25 | 2150888746303076 |
| 26 | 10122100177312089 |
| 27 | 47728242477117961 |
[1,2,6,19,68,251,983,3924,16210,67836,290213, 1253258,5495220,24266747,108356043,486533258, 2202981039,10019758277,45870934468,210776167079, 973568507191,4510808438116,20988565551476, 97915598003963,458399875204517,2150888746303076, 10122100177312089,47728242477117961] |