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 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 78 |
| 5 | 282 |
| 6 | 1187 |
| 7 | 4428 |
| 8 | 19175 |
| 9 | 72820 |
| 10 | 319493 |
| 11 | 1227712 |
| 12 | 5424359 |
| 13 | 21018514 |
| 14 | 93252862 |
| 15 | 363563668 |
| 16 | 1617342486 |
| 17 | 6334904252 |
| 18 | 28232695584 |
| 19 | 110982722888 |
| 20 | 495257577162 |