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 | 3 |
| 2 | 21 |
| 3 | 102 |
| 4 | 525 |
| 5 | 2334 |
| 6 | 11100 |
| 7 | 47496 |
| 8 | 210756 |
| 9 | 886080 |
| 10 | 3759114 |
| 11 | 15378051 |
| 12 | 63685767 |
| 13 | 255417357 |
| 14 | 1030081827 |
| 15 | 4078689249 |
| 16 | 16150234665 |
| 17 | 62991117084 |
| 18 | 245948154087 |
| 19 | 947944122906 |
| 20 | 3653360869998 |
| 21 | 13946363438502 |
| 22 | 53149517598207 |
| 23 | 200994216333375 |
| 24 | 759191650345380 |