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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 26 |
| 3 | 212 |
| 4 | 2046 |
| 5 | 22588 |
| 6 | 278942 |
| 7 | 3792916 |
| 8 | 56128254 |
| 9 | 895795692 |
| 10 | 15307847614 |
| 11 | 278435732484 |
| 12 | 5364073445278 |
| 13 | 108994074306268 |
| 14 | 2327475127169182 |
| 15 | 52069279762495220 |
| 16 | 1217024509006768574 |
| 17 | 29647115491635327180 |
| 18 | 751085909757123127294 |
| 19 | 19750410883486281805028 |
[1,4,26,212,2046,22588,278942,3792916,56128254, 895795692,15307847614,278435732484,5364073445278, 108994074306268,2327475127169182, 52069279762495220,1217024509006768574, 29647115491635327180,751085909757123127294, 19750410883486281805028] |