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 | 45 |
| 4 | 395 |
| 5 | 3775 |
| 6 | 38146 |
| 7 | 400826 |
| 8 | 4335455 |
| 9 | 47951065 |
| 10 | 539823620 |
| 11 | 6165377836 |
| 12 | 71261299056 |
| 13 | 831990025420 |
| 14 | 9797505040130 |
| 15 | 116235417614900 |
| 16 | 1387958781395535 |
| 17 | 16668362761081560 |
| 18 | 201190667288072005 |
| 19 | 2439418470063468505 |
| 20 | 29698136499328762445 |