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 | 15 |
| 4 | 105 |
| 5 | 945 |
| 6 | 3465 |
| 7 | 14857 |
| 8 | 72905 |
| 9 | 393565 |
| 10 | 2152693 |
| 11 | 10317169 |
| 12 | 49808117 |
| 13 | 247455873 |
| 14 | 1256019673 |
| 15 | 6371895677 |
| 16 | 31696702545 |
| 17 | 157383838325 |
| 18 | 785587613797 |
| 19 | 3938599251649 |
| 20 | 19742522444733 |
| 21 | 98655068282297 |
| 22 | 492637126850897 |
| 23 | 2462204077446773 |
| 24 | 12316715419452585 |