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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 14 |
| 5 | 80 |
| 6 | 558 |
| 7 | 4522 |
| 8 | 41864 |
| 9 | 436032 |
| 10 | 5046680 |
| 11 | 64251176 |
| 12 | 892361520 |
| 13 | 13426491520 |
| 14 | 217555171568 |
| 15 | 3776935252560 |
| 16 | 69942048682112 |
| 17 | 1376150998836224 |
| 18 | 28669321699355520 |
| 19 | 630448829825395840 |
| 20 | 14593473117397510400 |
| 21 | 354696400190943197184 |
| 22 | 9031466708133617225984 |