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 | 11 |
| 4 | 53 |
| 5 | 305 |
| 6 | 2051 |
| 7 | 15731 |
| 8 | 135697 |
| 9 | 1300869 |
| 10 | 13726431 |
| 11 | 158137851 |
| 12 | 1975599321 |
| 13 | 26607158781 |
| 14 | 384347911211 |
| 15 | 5928465081703 |
| 16 | 97262304328573 |
| 17 | 1691274884085061 |
| 18 | 31073791192091251 |
| 19 | 601539400910369671 |
| 20 | 12238270940611270161 |
| 21 | 261071590963047040241 |