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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 32 |
| 4 | 256 |
| 5 | 2712 |
| 6 | 37744 |
| 7 | 645752 |
| 8 | 13371264 |
| 9 | 327748832 |
| 10 | 9332342944 |
| 11 | 304875611328 |
| 12 | 11298403070464 |
| 13 | 470279355784448 |
| 14 | 21809054992366464 |
| 15 | 1118931830122060928 |
| 16 | 63115145120561606656 |
| 17 | 3892675200470654980608 |
| 18 | 261242029823318546162176 |
| 19 | 18994387868664467440590848 |
| 20 | 1490356266852194536099393536 |
| 21 | 125747158151444491631754033152 |
[1,2,6,32,256,2712,37744,645752,13371264, 327748832,9332342944,304875611328,11298403070464, 470279355784448,21809054992366464, 1118931830122060928,63115145120561606656, 3892675200470654980608,261242029823318546162176, 18994387868664467440590848, 1490356266852194536099393536, 125747158151444491631754033152] |