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 | 0 |
| 1 | 1 |
| 2 | 10 |
| 3 | 69 |
| 4 | 406 |
| 5 | 2186 |
| 6 | 11124 |
| 7 | 54445 |
| 8 | 259006 |
| 9 | 1205790 |
| 10 | 5519020 |
| 11 | 24918306 |
| 12 | 111250140 |
| 13 | 492051124 |
| 14 | 2159081192 |
| 15 | 9409526397 |
| 16 | 40766269774 |
| 17 | 175707380630 |
| 18 | 753876367356 |
| 19 | 3221460111958 |
| 20 | 13716223138388 |
| 21 | 58210889582796 |