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 | 1 |
| 3 | 4 |
| 4 | 15 |
| 5 | 74 |
| 6 | 427 |
| 7 | 2901 |
| 8 | 22624 |
| 9 | 199095 |
| 10 | 1951127 |
| 11 | 21072175 |
| 12 | 248651668 |
| 13 | 3182741351 |
| 14 | 43921830648 |
| 15 | 650043093588 |
| 16 | 10270680878694 |
| 17 | 172547438762056 |
| 18 | 3071344409964594 |
| 19 | 57741274907334370 |
| 20 | 1143277243165220534 |