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 | 0 |
| 1 | 1 |
| 2 | 18 |
| 3 | 152 |
| 4 | 1110 |
| 5 | 8254 |
| 6 | 66050 |
| 7 | 578466 |
| 8 | 5557246 |
| 9 | 58381646 |
| 10 | 667481754 |
| 11 | 8262618730 |
| 12 | 110195259446 |
| 13 | 1576108225446 |
| 14 | 24075493095346 |
| 15 | 391282065519074 |
| 16 | 6742907753730030 |
| 17 | 122830141805635966 |
| 18 | 2358555332361509066 |
| 19 | 47617194132209848026 |
| 20 | 1008436738991020480294 |