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 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 60 |
| 6 | 240 |
| 7 | 1085 |
| 8 | 5012 |
| 9 | 23730 |
| 10 | 121440 |
| 11 | 685707 |
| 12 | 4144668 |
| 13 | 25614589 |
| 14 | 159141892 |
| 15 | 1012740885 |
| 16 | 6805631232 |
| 17 | 48872707006 |
| 18 | 369227821608 |
| 19 | 2853779791619 |
| 20 | 22131042288980 |
| 21 | 172055270717463 |
| 22 | 1362017827326860 |
| 23 | 11208504802237327 |
| 24 | 96939147303239304 |
| 25 | 875473007351905045 |