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 | 2 |
| 2 | 3 |
| 3 | 9 |
| 4 | 26 |
| 5 | 135 |
| 6 | 1124 |
| 7 | 11225 |
| 8 | 143600 |
| 9 | 2156862 |
| 10 | 36069006 |
| 11 | 681844857 |
| 12 | 14387370477 |
| 13 | 327462904319 |
| 14 | 8171705457024 |
| 15 | 221137571070305 |
| 16 | 6373582250114091 |
| 17 | 197210862517274355 |
| 18 | 6521583445100185049 |
| 19 | 227168823675390365225 |
| 20 | 8396976723995537706278 |
| 21 | 327880018217851412105973 |