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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 103 |
| 5 | 604 |
| 6 | 3728 |
| 7 | 23866 |
| 8 | 157015 |
| 9 | 1055121 |
| 10 | 7211227 |
| 11 | 49970893 |
| 12 | 350283538 |
| 13 | 2479386646 |
| 14 | 17696379769 |
| 15 | 127220129807 |
| 16 | 920376055978 |
| 17 | 6695598216385 |
| 18 | 48950677790253 |
| 19 | 359456740745360 |
| 20 | 2650089982411601 |
| 21 | 19608110285151138 |
| 22 | 145555836451997536 |
| 23 | 1083723594296492362 |
[1,1,4,19,103,604,3728,23866,157015,1055121, 7211227,49970893,350283538,2479386646,17696379769, 127220129807,920376055978,6695598216385, 48950677790253,359456740745360,2650089982411601, 19608110285151138,145555836451997536, 1083723594296492362] |