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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 44 |
| 5 | 262 |
| 6 | 1938 |
| 7 | 15600 |
| 8 | 145086 |
| 9 | 1461888 |
| 10 | 16438446 |
| 11 | 198598860 |
| 12 | 2623055166 |
| 13 | 36933441912 |
| 14 | 560697617214 |
| 15 | 9014444990964 |
| 16 | 154698782105070 |
| 17 | 2795947673216544 |
| 18 | 53529558912435438 |
| 19 | 1074325981318055676 |
| 20 | 22703327631819203166 |
| 21 | 500976898248191064840 |
[1,2,8,44,262,1938,15600,145086,1461888,16438446, 198598860,2623055166,36933441912,560697617214, 9014444990964,154698782105070,2795947673216544, 53529558912435438,1074325981318055676, 22703327631819203166,500976898248191064840] |