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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 20 |
| 4 | 69 |
| 5 | 178 |
| 6 | 571 |
| 7 | 1451 |
| 8 | 4108 |
| 9 | 10480 |
| 10 | 27578 |
| 11 | 68401 |
| 12 | 172818 |
| 13 | 417979 |
| 14 | 1017575 |
| 15 | 2410964 |
| 16 | 5702481 |
| 17 | 13228877 |
| 18 | 30573978 |
| 19 | 69594694 |
| 20 | 157597162 |
| 21 | 352694078 |
| 22 | 784615466 |
| 23 | 1728604925 |
| 24 | 3785636280 |
| 25 | 8221695626 |
| 26 | 17751593170 |
| 27 | 38051212654 |
| 28 | 81103710142 |
| 29 | 171757084527 |
[1,1,7,20,69,178,571,1451,4108,10480,27578,68401, 172818,417979,1017575,2410964,5702481,13228877, 30573978,69594694,157597162,352694078,784615466, 1728604925,3785636280,8221695626,17751593170, 38051212654,81103710142,171757084527] |