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 | 3 |
| 3 | 12 |
| 4 | 61 |
| 5 | 375 |
| 6 | 2697 |
| 7 | 22176 |
| 8 | 204977 |
| 9 | 2102445 |
| 10 | 23685615 |
| 11 | 290642220 |
| 12 | 3857751573 |
| 13 | 55063797243 |
| 14 | 840956549517 |
| 15 | 13682498891040 |
| 16 | 236257301424225 |
| 17 | 4314883836968505 |
| 18 | 83102361300891963 |
| 19 | 1683252077760375660 |
| 20 | 35770269996769203405 |
| 21 | 795749735451309432255 |