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 | 2 |
| 2 | 10 |
| 3 | 60 |
| 4 | 390 |
| 5 | 2660 |
| 6 | 18772 |
| 7 | 138984 |
| 8 | 1107686 |
| 9 | 9576100 |
| 10 | 87944188 |
| 11 | 830857464 |
| 12 | 7876505340 |
| 13 | 73967614584 |
| 14 | 685644645896 |
| 15 | 6289047266480 |
| 16 | 57465415636166 |
| 17 | 528315307772004 |
| 18 | 4947263762389484 |
| 19 | 47785581838822232 |
| 20 | 480797992896880788 |
| 21 | 5058812497153271912 |