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 | 6 |
| 3 | 54 |
| 4 | 542 |
| 5 | 5955 |
| 6 | 69114 |
| 7 | 835140 |
| 8 | 10391843 |
| 9 | 132262619 |
| 10 | 1713785727 |
| 11 | 22531557603 |
| 12 | 299817809184 |
| 13 | 4030217936308 |
| 14 | 54646151953660 |
| 15 | 746513545616000 |
| 16 | 10264746883787021 |
| 17 | 141955200254335604 |
| 18 | 1973170863256461516 |
| 19 | 27551902179444882489 |
| 20 | 386288077655575999571 |
| 21 | 5435910477286670671340 |