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 | 13 |
| 4 | 73 |
| 5 | 501 |
| 6 | 4051 |
| 7 | 37633 |
| 8 | 394353 |
| 9 | 4596553 |
| 10 | 55312291 |
| 11 | 744239541 |
| 12 | 10793656633 |
| 13 | 167689950013 |
| 14 | 2775839905203 |
| 15 | 48726598412521 |
| 16 | 903159189729121 |
| 17 | 17607070923233553 |
| 18 | 359702718305842243 |
| 19 | 7673827033741108573 |
| 20 | 171586828999546057641 |
| 21 | 3999150173195168500741 |