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Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 15 |
| 5 | 42 |
| 6 | 143 |
| 7 | 399 |
| 8 | 1190 |
| 9 | 4209 |
| 10 | 13130 |
| 11 | 41591 |
| 12 | 118590 |
| 13 | 404471 |
| 14 | 1158696 |
| 15 | 3893831 |
| 16 | 12222320 |
| 17 | 39428991 |
| 18 | 123471920 |
| 19 | 397952081 |
| 20 | 1297210320 |
[1,2,6,15,42,143,399,1190,4209,13130,41591,118590, 404471,1158696,3893831,12222320,39428991, 123471920,397952081,1297210320] |