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 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 18 |
| 6 | 97 |
| 7 | 620 |
| 8 | 4570 |
| 9 | 38270 |
| 10 | 358778 |
| 11 | 3722325 |
| 12 | 42341447 |
| 13 | 523975411 |
| 14 | 7008171125 |
| 15 | 100742459918 |
| 16 | 1548915321246 |
| 17 | 25363488385399 |
| 18 | 440690610696307 |
| 19 | 8097689971544645 |
| 20 | 156892743198677493 |
| 21 | 3196689642673053919 |