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 | 3 |
| 3 | 16 |
| 4 | 63 |
| 5 | 275 |
| 6 | 1152 |
| 7 | 4901 |
| 8 | 20727 |
| 9 | 87856 |
| 10 | 372075 |
| 11 | 1576279 |
| 12 | 6676992 |
| 13 | 28284569 |
| 14 | 119814747 |
| 15 | 507544400 |
| 16 | 2149990983 |
| 17 | 9107510539 |
| 18 | 38580029568 |
| 19 | 163427634589 |
| 20 | 692290558575 |
| 21 | 2932589884016 |
| 22 | 12422650070163 |
| 23 | 52623190204271 |
| 24 | 222915410823168 |
| 25 | 944284833600625 |
| 26 | 4000054745057907 |
| 27 | 16944503814103696 |
| 28 | 71778070001033487 |