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 | 4 |
| 2 | 20 |
| 3 | 80 |
| 4 | 305 |
| 5 | 1072 |
| 6 | 3622 |
| 7 | 11676 |
| 8 | 36450 |
| 9 | 110240 |
| 10 | 324936 |
| 11 | 935076 |
| 12 | 2635338 |
| 13 | 7285560 |
| 14 | 19795370 |
| 15 | 52930360 |
| 16 | 139462956 |
| 17 | 362471020 |
| 18 | 930186694 |
| 19 | 2358867240 |
| 20 | 5915606398 |
| 21 | 14680528648 |
| 22 | 36073675792 |
| 23 | 87816701332 |
| 24 | 211891552280 |
| 25 | 506981067168 |
| 26 | 1203337174120 |
| 27 | 2834401172172 |