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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 42 |
| 5 | 130 |
| 6 | 590 |
| 7 | 2065 |
| 8 | 9590 |
| 9 | 36246 |
| 10 | 169302 |
| 11 | 662508 |
| 12 | 3151302 |
| 13 | 12716418 |
| 14 | 60766134 |
| 15 | 249975297 |
| 16 | 1204668894 |
| 17 | 5046138526 |
| 18 | 24387184250 |
| 19 | 103327379584 |
| 20 | 502209024746 |
| 21 | 2152035376998 |
| 22 | 10480335520954 |
| 23 | 45276651995848 |
| 24 | 221246448525258 |
| 25 | 963621977231330 |
| 26 | 4715103886462790 |
| 27 | 20657384214505530 |
[1,1,4,9,42,130,590,2065,9590,36246,169302,662508, 3151302,12716418,60766134,249975297,1204668894, 5046138526,24387184250,103327379584,502209024746, 2152035376998,10480335520954,45276651995848, 221246448525258,963621977231330,4715103886462790, 20657384214505530] |