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 | 10 |
| 4 | 45 |
| 5 | 251 |
| 6 | 1624 |
| 7 | 11908 |
| 8 | 97545 |
| 9 | 880660 |
| 10 | 8664546 |
| 11 | 92096731 |
| 12 | 1050304775 |
| 13 | 12778138842 |
| 14 | 165033693175 |
| 15 | 2253204163256 |
| 16 | 32401745953105 |
| 17 | 489207829112931 |
| 18 | 7733130368443057 |
| 19 | 127664099576228184 |
| 20 | 2196149923000824756 |