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) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 28 |
| 4 | 244 |
| 5 | 1680 |
| 6 | 10214 |
| 7 | 57476 |
| 8 | 305476 |
| 9 | 1553632 |
| 10 | 7641218 |
| 11 | 36608932 |
| 12 | 171666468 |
| 13 | 790650724 |
| 14 | 3586822020 |
| 15 | 16062938368 |
| 16 | 71135451440 |
| 17 | 311964025352 |
| 18 | 1356392904818 |
| 19 | 5852609697844 |
| 20 | 25081266854732 |