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 | 2 |
| 2 | 4 |
| 3 | 11 |
| 4 | 31 |
| 5 | 309 |
| 6 | 1028 |
| 7 | 12251 |
| 8 | 43390 |
| 9 | 564163 |
| 10 | 28192750 |
| 11 | 105097565 |
| 12 | 5586502348 |
| 13 | 80316571436 |
| 14 | 305761713237 |
| 15 | 4461632979717 |
| 16 | 252252704148404 |
| 17 | 14458792895301660 |
| 18 | 55890484045084135 |
| 19 | 3249254387052557215 |
| 20 | 48995571600129458363 |
| 21 | 190499823401327905601 |