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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 13 |
| 3 | 50 |
| 4 | 173 |
| 5 | 613 |
| 6 | 2149 |
| 7 | 7557 |
| 8 | 26543 |
| 9 | 93264 |
| 10 | 327657 |
| 11 | 1151183 |
| 12 | 4044478 |
| 13 | 14209634 |
| 14 | 49923211 |
| 15 | 175397097 |
| 16 | 616229093 |
| 17 | 2165020570 |
| 18 | 7606447024 |
| 19 | 26724012524 |
| 20 | 93890464368 |
| 21 | 329868851103 |
| 22 | 1158940469863 |
| 23 | 4071748539926 |
| 24 | 14305425173111 |
[0,4,13,50,173,613,2149,7557,26543,93264,327657, 1151183,4044478,14209634,49923211,175397097, 616229093,2165020570,7606447024,26724012524, 93890464368,329868851103,1158940469863, 4071748539926,14305425173111] |