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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 52 |
| 5 | 190 |
| 6 | 855 |
| 7 | 3448 |
| 8 | 15875 |
| 9 | 67678 |
| 10 | 316366 |
| 11 | 1396314 |
| 12 | 6597636 |
| 13 | 29809522 |
| 14 | 141975693 |
| 15 | 652322186 |
| 16 | 3125882456 |
| 17 | 14543234380 |
| 18 | 70027024190 |
| 19 | 328968821688 |
| 20 | 1590200013363 |
| 21 | 7527833432944 |
| 22 | 36505703751706 |
| 23 | 173889579216954 |
| 24 | 845532639405358 |
| 25 | 4048203059271664 |
| 26 | 19729132295352556 |
| 27 | 94862396799568710 |
[1,1,4,12,52,190,855,3448,15875,67678,316366, 1396314,6597636,29809522,141975693,652322186, 3125882456,14543234380,70027024190,328968821688, 1590200013363,7527833432944,36505703751706, 173889579216954,845532639405358,4048203059271664, 19729132295352556,94862396799568710] |