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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 114 |
| 6 | 628 |
| 7 | 4062 |
| 8 | 30360 |
| 9 | 255186 |
| 10 | 2414292 |
| 11 | 25350954 |
| 12 | 292378968 |
| 13 | 3673917102 |
| 14 | 49928069188 |
| 15 | 729534877758 |
| 16 | 11403682481112 |
| 17 | 189862332575658 |
| 18 | 3354017704180052 |
| 19 | 62654508729565554 |
| 20 | 1233924707891272728 |
| 21 | 25550498290562247438 |