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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 88 |
| 5 | 520 |
| 6 | 2654 |
| 7 | 12376 |
| 8 | 54612 |
| 9 | 232788 |
| 10 | 970538 |
| 11 | 3988644 |
| 12 | 16239088 |
| 13 | 65709280 |
| 14 | 264814166 |
| 15 | 1064414128 |
| 16 | 4271035692 |
| 17 | 17118683052 |
| 18 | 68563527650 |
| 19 | 274481537148 |
| 20 | 1098506723080 |
| 21 | 4395504614584 |
| 22 | 17585769696206 |
| 23 | 70352578566664 |
| 24 | 281434319454084 |
| 25 | 1125797816327940 |
[0,2,12,88,520,2654,12376,54612,232788,970538, 3988644,16239088,65709280,264814166,1064414128, 4271035692,17118683052,68563527650,274481537148, 1098506723080,4395504614584,17585769696206, 70352578566664,281434319454084,1125797816327940] |