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 | 3 |
| 3 | 21 |
| 4 | 147 |
| 5 | 1323 |
| 6 | 12618 |
| 7 | 131085 |
| 8 | 1430187 |
| 9 | 16297347 |
| 10 | 191987562 |
| 11 | 2325379147 |
| 12 | 28821761290 |
| 13 | 364290802138 |
| 14 | 4682375323044 |
| 15 | 61067639131197 |
| 16 | 806671205158587 |
| 17 | 10776418254992139 |
| 18 | 145413196382253114 |
| 19 | 1979833455619072515 |
| 20 | 27174458892459331530 |
| 21 | 375722890152963114330 |