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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 7 |
| 4 | 30 |
| 5 | 75 |
| 6 | 323 |
| 7 | 927 |
| 8 | 4084 |
| 9 | 12757 |
| 10 | 57357 |
| 11 | 190323 |
| 12 | 863932 |
| 13 | 2990215 |
| 14 | 13742390 |
| 15 | 49151253 |
| 16 | 227407578 |
| 17 | 834395673 |
| 18 | 3888507313 |
| 19 | 14572098227 |
| 20 | 68261017116 |
| 21 | 260231521603 |
| 22 | 1224649653002 |
| 23 | 4738562044311 |
| 24 | 22388087279914 |
| 25 | 87710572097589 |
| 26 | 415756729437735 |
| 27 | 1646822285537643 |
| 28 | 7829736984834466 |
[1,1,4,7,30,75,323,927,4084,12757,57357,190323, 863932,2990215,13742390,49151253,227407578, 834395673,3888507313,14572098227,68261017116, 260231521603,1224649653002,4738562044311, 22388087279914,87710572097589,415756729437735, 1646822285537643,7829736984834466] |