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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 10 |
| 3 | 26 |
| 4 | 66 |
| 5 | 168 |
| 6 | 426 |
| 7 | 1078 |
| 8 | 2722 |
| 9 | 6862 |
| 10 | 17274 |
| 11 | 43432 |
| 12 | 109086 |
| 13 | 273734 |
| 14 | 686334 |
| 15 | 1719604 |
| 16 | 4305666 |
| 17 | 10774550 |
| 18 | 26948142 |
| 19 | 67367456 |
| 20 | 168337622 |
| 21 | 420472716 |
| 22 | 1049866442 |
| 23 | 2620488898 |
| 24 | 6538734758 |
| 25 | 16310909604 |
| 26 | 40676600026 |
| 27 | 101414764862 |
| 28 | 252787228590 |
| 29 | 629960214066 |
[1,4,10,26,66,168,426,1078,2722,6862,17274,43432, 109086,273734,686334,1719604,4305666,10774550, 26948142,67367456,168337622,420472716,1049866442, 2620488898,6538734758,16310909604,40676600026, 101414764862,252787228590,629960214066] |