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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 10 |
| 3 | 28 |
| 4 | 74 |
| 5 | 202 |
| 6 | 534 |
| 7 | 1442 |
| 8 | 3822 |
| 9 | 10258 |
| 10 | 27202 |
| 11 | 72718 |
| 12 | 192840 |
| 13 | 514228 |
| 14 | 1363342 |
| 15 | 3629316 |
| 16 | 9619264 |
| 17 | 25575326 |
| 18 | 67765590 |
| 19 | 180001304 |
| 20 | 476807826 |
| 21 | 1265567600 |
| 22 | 3351529410 |
| 23 | 8890447682 |
| 24 | 23538665948 |
| 25 | 62409037914 |
| 26 | 165202281046 |
[1,4,10,28,74,202,534,1442,3822,10258,27202,72718, 192840,514228,1363342,3629316,9619264,25575326, 67765590,180001304,476807826,1265567600, 3351529410,8890447682,23538665948,62409037914, 165202281046] |