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 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 64 |
| 5 | 321 |
| 6 | 1092 |
| 7 | 5461 |
| 8 | 16384 |
| 9 | 81921 |
| 10 | 278532 |
| 11 | 1392661 |
| 12 | 4210752 |
| 13 | 21053761 |
| 14 | 71582788 |
| 15 | 357913941 |
| 16 | 1073741824 |
| 17 | 5368709121 |
| 18 | 18253611012 |
| 19 | 91268055061 |
| 20 | 275951648832 |
| 21 | 1379758244161 |
| 22 | 4691178030148 |
| 23 | 23455890150741 |