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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 79 |
| 5 | 304 |
| 6 | 1223 |
| 7 | 5028 |
| 8 | 21047 |
| 9 | 89251 |
| 10 | 383518 |
| 11 | 1663928 |
| 12 | 7276480 |
| 13 | 32045842 |
| 14 | 142037287 |
| 15 | 632872830 |
| 16 | 2832858397 |
| 17 | 12734620947 |
| 18 | 57464148718 |
| 19 | 260162526888 |
| 20 | 1181426526600 |
| 21 | 5380086708793 |
| 22 | 24562294842043 |
| 23 | 112393730436929 |
| 24 | 515397881372591 |
| 25 | 2368117618280042 |
| 26 | 10900588201137940 |
| 27 | 50260446215458211 |
[1,2,6,21,79,304,1223,5028,21047,89251,383518, 1663928,7276480,32045842,142037287,632872830, 2832858397,12734620947,57464148718,260162526888, 1181426526600,5380086708793,24562294842043, 112393730436929,515397881372591,2368117618280042, 10900588201137940,50260446215458211] |