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 | 67 |
| 5 | 471 |
| 6 | 3271 |
| 7 | 31333 |
| 8 | 299223 |
| 9 | 3291487 |
| 10 | 39020911 |
| 11 | 543960561 |
| 12 | 7466726983 |
| 13 | 118551513523 |
| 14 | 1917378505407 |
| 15 | 32405299019941 |
| 16 | 608246253790591 |
| 17 | 12219834139189263 |
| 18 | 253767339725277823 |
| 19 | 5591088918313739017 |
| 20 | 126036990829657056711 |
| 21 | 2956563745611392385211 |