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 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 24 |
| 7 | 144 |
| 8 | 1028 |
| 9 | 8371 |
| 10 | 76528 |
| 11 | 776208 |
| 12 | 8649166 |
| 13 | 105025576 |
| 14 | 1380336142 |
| 15 | 19521896862 |
| 16 | 295617295327 |
| 17 | 4772107767406 |
| 18 | 81807561726951 |
| 19 | 1484222905617530 |
| 20 | 28412267050392706 |
| 21 | 572304236300767348 |