This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 33 |
| 4 | 273 |
| 5 | 2721 |
| 6 | 31701 |
| 7 | 421905 |
| 8 | 6302913 |
| 9 | 104270913 |
| 10 | 1889862021 |
| 11 | 37204038081 |
| 12 | 789866524305 |
| 13 | 17977594555233 |
| 14 | 436435929785493 |
| 15 | 11251798888929201 |
| 16 | 306889765901872641 |
| 17 | 8825681949708120705 |
| 18 | 266828094135981378693 |
| 19 | 8458295877281844310113 |