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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 31 |
| 4 | 175 |
| 5 | 991 |
| 6 | 5881 |
| 7 | 35617 |
| 8 | 219871 |
| 9 | 1376095 |
| 10 | 8710537 |
| 11 | 55644337 |
| 12 | 358198369 |
| 13 | 2320792657 |
| 14 | 15120204295 |
| 15 | 98984058271 |
| 16 | 650725327231 |
| 17 | 4293779332927 |
| 18 | 28425752310361 |
| 19 | 188739799967425 |
| 20 | 1256510215733185 |
| 21 | 8385127334900305 |
| 22 | 56078904057164215 |
| 23 | 375796823748323215 |
[1,1,7,31,175,991,5881,35617,219871,1376095, 8710537,55644337,358198369,2320792657,15120204295, 98984058271,650725327231,4293779332927, 28425752310361,188739799967425,1256510215733185, 8385127334900305,56078904057164215, 375796823748323215] |