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 | 2 |
| 2 | 6 |
| 3 | 22 |
| 4 | 94 |
| 5 | 462 |
| 6 | 2606 |
| 7 | 16862 |
| 8 | 124782 |
| 9 | 1048990 |
| 10 | 9921550 |
| 11 | 104447550 |
| 12 | 1211190638 |
| 13 | 15329157278 |
| 14 | 210093682254 |
| 15 | 3097760346238 |
| 16 | 48869022535726 |
| 17 | 821007386273118 |
| 18 | 14630266558195214 |
| 19 | 275575669958063678 |
| 20 | 5469996402416702958 |
| 21 | 114107289124208861470 |