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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 91 |
| 6 | 407 |
| 7 | 1921 |
| 8 | 9429 |
| 9 | 47683 |
| 10 | 246901 |
| 11 | 1303346 |
| 12 | 6992087 |
| 13 | 38031159 |
| 14 | 209348857 |
| 15 | 1164616227 |
| 16 | 6540112446 |
| 17 | 37040976542 |
| 18 | 211423703225 |
| 19 | 1215450693258 |
| 20 | 7034282005208 |
| 21 | 40966313765380 |
| 22 | 240003678300088 |
| 23 | 1414101405300096 |
[1,1,2,6,22,91,407,1921,9429,47683,246901,1303346, 6992087,38031159,209348857,1164616227,6540112446, 37040976542,211423703225,1215450693258, 7034282005208,40966313765380,240003678300088, 1414101405300096] |