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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 9 |
| 5 | 30 |
| 6 | 89 |
| 7 | 258 |
| 8 | 720 |
| 9 | 2016 |
| 10 | 5583 |
| 11 | 15546 |
| 12 | 43215 |
| 13 | 120750 |
| 14 | 338001 |
| 15 | 950030 |
| 16 | 2677770 |
| 17 | 7573350 |
| 18 | 21478632 |
| 19 | 61088874 |
| 20 | 174179133 |
| 21 | 497812378 |
| 22 | 1425832077 |
| 23 | 4092087522 |
| 24 | 11765778330 |
| 25 | 33887517840 |
| 26 | 97756266615 |
| 27 | 282414622728 |
| 28 | 816999371955 |
| 29 | 2366509198350 |
| 30 | 6862929885407 |