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 | 15 |
| 4 | 82 |
| 5 | 549 |
| 6 | 3957 |
| 7 | 31423 |
| 8 | 262905 |
| 9 | 2309655 |
| 10 | 20954053 |
| 11 | 195219912 |
| 12 | 1855139472 |
| 13 | 17913275558 |
| 14 | 175183126884 |
| 15 | 1731034436637 |
| 16 | 17250012004590 |
| 17 | 173095950538881 |
| 18 | 1746875271992760 |
| 19 | 17712083908168204 |
| 20 | 180276161806773003 |
| 21 | 1840572737915529150 |
| 22 | 18838475627464850819 |