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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 40 |
| 5 | 119 |
| 6 | 539 |
| 7 | 1841 |
| 8 | 8364 |
| 9 | 30955 |
| 10 | 141649 |
| 11 | 549875 |
| 12 | 2542866 |
| 13 | 10164631 |
| 14 | 47527100 |
| 15 | 193802541 |
| 16 | 914717352 |
| 17 | 3788393117 |
| 18 | 18005282017 |
| 19 | 75561381227 |
| 20 | 360910284426 |
| 21 | 1531898228495 |
| 22 | 7344956490924 |
| 23 | 31475455042689 |
| 24 | 151413448157436 |
| 25 | 654028472348391 |
| 26 | 3155668890434889 |
| 27 | 13722284292332989 |
[1,1,4,9,40,119,539,1841,8364,30955,141649,549875, 2542866,10164631,47527100,193802541,914717352, 3788393117,18005282017,75561381227,360910284426, 1531898228495,7344956490924,31475455042689, 151413448157436,654028472348391,3155668890434889, 13722284292332989] |