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 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 14 |
| 4 | 58 |
| 5 | 292 |
| 6 | 1754 |
| 7 | 12280 |
| 8 | 98242 |
| 9 | 884180 |
| 10 | 8841802 |
| 11 | 97259824 |
| 12 | 1167117890 |
| 13 | 15172532572 |
| 14 | 212415456010 |
| 15 | 3186231840152 |
| 16 | 50979709442434 |
| 17 | 866655060521380 |
| 18 | 15599791089384842 |
| 19 | 296396030698312000 |
| 20 | 5927920613966240002 |
| 21 | 124486332893291040044 |