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 | 69 |
| 5 | 421 |
| 6 | 2867 |
| 7 | 21477 |
| 8 | 175769 |
| 9 | 1567273 |
| 10 | 15213955 |
| 11 | 160727997 |
| 12 | 1846282381 |
| 13 | 23013527421 |
| 14 | 310284575683 |
| 15 | 4506744095141 |
| 16 | 70199956070705 |
| 17 | 1167389338452753 |
| 18 | 20636801363971139 |
| 19 | 386304535988493101 |
| 20 | 7630926750477398037 |
| 21 | 158584458024427667669 |