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 | 0 |
| 2 | 1 |
| 3 | 15 |
| 4 | 127 |
| 5 | 1006 |
| 6 | 8230 |
| 7 | 70320 |
| 8 | 614821 |
| 9 | 5453140 |
| 10 | 48982456 |
| 11 | 444608278 |
| 12 | 4070532710 |
| 13 | 37535715441 |
| 14 | 348245215460 |
| 15 | 3247889171908 |
| 16 | 30429496751905 |
| 17 | 286235215995588 |
| 18 | 2702000272361599 |
| 19 | 25586688305447928 |
| 20 | 242978340446949438 |
| 21 | 2313264023790027111 |
| 22 | 22074118786158858975 |