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 | 9 |
| 3 | 109 |
| 4 | 1457 |
| 5 | 18231 |
| 6 | 205837 |
| 7 | 2112384 |
| 8 | 20341201 |
| 9 | 189013501 |
| 10 | 1725377947 |
| 11 | 15622028115 |
| 12 | 140950202021 |
| 13 | 1269874954518 |
| 14 | 11433967343409 |
| 15 | 102926130336136 |
| 16 | 926421241593985 |
| 17 | 8338171770377449 |
| 18 | 75045297684511343 |
| 19 | 675415983886759045 |
| 20 | 6078784024809901485 |