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 | 19 |
| 4 | 145 |
| 5 | 1401 |
| 6 | 16051 |
| 7 | 213403 |
| 8 | 3223809 |
| 9 | 54514225 |
| 10 | 1019601091 |
| 11 | 20890209891 |
| 12 | 465156779473 |
| 13 | 11181638663209 |
| 14 | 288536019179955 |
| 15 | 7953590111627371 |
| 16 | 233211718410856321 |
| 17 | 7246720953253750113 |
| 18 | 237849724555558441219 |
| 19 | 8221578401608012672435 |
| 20 | 298505383888840158941841 |