| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 55 |
| 4 | 415 |
| 5 | 3391 |
| 6 | 28681 |
| 7 | 248137 |
| 8 | 2186815 |
| 9 | 19546975 |
| 10 | 176703337 |
| 11 | 1612210777 |
| 12 | 14823083089 |
| 13 | 137176167025 |
| 14 | 1276548044695 |
| 15 | 11936862061495 |
| 16 | 112092031526335 |
| 17 | 1056512066133055 |
| 18 | 9991003788000025 |
| 19 | 94760438267696425 |
| 20 | 901154863603211665 |
[1,7,55,415,3391,28681,248137,2186815,19546975, 176703337,1612210777,14823083089,137176167025, 1276548044695,11936862061495,112092031526335, 1056512066133055,9991003788000025, 94760438267696425,901154863603211665] |