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 | 2 |
| 3 | 23 |
| 4 | 147 |
| 5 | 748 |
| 6 | 3414 |
| 7 | 14719 |
| 8 | 61495 |
| 9 | 252364 |
| 10 | 1024938 |
| 11 | 4137207 |
| 12 | 16639339 |
| 13 | 66775964 |
| 14 | 267631726 |
| 15 | 1071801407 |
| 16 | 4290282671 |
| 17 | 17168559452 |
| 18 | 68692172578 |
| 19 | 274811988823 |
| 20 | 1099352487299 |
| 21 | 4397662311948 |
| 22 | 17591258505542 |
| 23 | 70366504900671 |
| 24 | 281469570617703 |
| 25 | 1125886855379628 |