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 | 7 |
| 4 | 49 |
| 5 | 364 |
| 6 | 2548 |
| 7 | 18130 |
| 8 | 126910 |
| 9 | 890463 |
| 10 | 6234270 |
| 11 | 43655178 |
| 12 | 305586246 |
| 13 | 2139225879 |
| 14 | 14974581153 |
| 15 | 104822829531 |
| 16 | 733759913733 |
| 17 | 5136324781952 |
| 18 | 35954273473664 |
| 19 | 251679952469351 |
| 20 | 1761759667285457 |
| 21 | 12332317933624871 |