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 | 4 |
| 3 | 17 |
| 4 | 81 |
| 5 | 410 |
| 6 | 2169 |
| 7 | 11847 |
| 8 | 66306 |
| 9 | 378297 |
| 10 | 2192011 |
| 11 | 12864668 |
| 12 | 76313865 |
| 13 | 456837181 |
| 14 | 2756271064 |
| 15 | 16743326577 |
| 16 | 102319639173 |
| 17 | 628599899558 |
| 18 | 3880049052441 |
| 19 | 24051163355499 |
| 20 | 149654739889478 |
| 21 | 934426798835377 |