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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 217 |
| 6 | 2470 |
| 7 | 35647 |
| 8 | 637129 |
| 9 | 13843948 |
| 10 | 360022957 |
| 11 | 11054457253 |
| 12 | 396003680518 |
| 13 | 16377463914091 |
| 14 | 774714094061221 |
| 15 | 41572230979229284 |
| 16 | 2512149910125036865 |
| 17 | 169831839578092130017 |
| 18 | 12769241823369505582150 |
| 19 | 1062122471116082751430087 |
| 20 | 97264621940872013476357969 |