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 | 4 |
| 3 | 21 |
| 4 | 165 |
| 5 | 1609 |
| 6 | 19236 |
| 7 | 266251 |
| 8 | 4175367 |
| 9 | 72705802 |
| 10 | 1387084926 |
| 11 | 28689560868 |
| 12 | 638068960017 |
| 13 | 15158039092293 |
| 14 | 382527449091778 |
| 15 | 10207466648995608 |
| 16 | 286876818184163613 |
| 17 | 8462814670769394769 |
| 18 | 261266723355912507073 |
| 19 | 8419093340955799898258 |
| 20 | 282519424041100564770142 |