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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 10 |
| 3 | 26 |
| 4 | 80 |
| 5 | 194 |
| 6 | 504 |
| 7 | 1442 |
| 8 | 3710 |
| 9 | 9536 |
| 10 | 26842 |
| 11 | 69014 |
| 12 | 178704 |
| 13 | 496602 |
| 14 | 1316204 |
| 15 | 3377206 |
| 16 | 9242898 |
| 17 | 24629944 |
| 18 | 63304540 |
| 19 | 172497622 |
| 20 | 462822414 |
| 21 | 1210912388 |
| 22 | 3177522724 |
| 23 | 8736822276 |
| 24 | 22617998204 |
| 25 | 59776061150 |
| 26 | 163702751968 |
| 27 | 433787373560 |
[1,4,10,26,80,194,504,1442,3710,9536,26842,69014, 178704,496602,1316204,3377206,9242898,24629944, 63304540,172497622,462822414,1210912388, 3177522724,8736822276,22617998204,59776061150, 163702751968,433787373560] |