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 | 9 |
| 3 | 53 |
| 4 | 253 |
| 5 | 1059 |
| 6 | 4043 |
| 7 | 14407 |
| 8 | 48639 |
| 9 | 157184 |
| 10 | 489872 |
| 11 | 1480608 |
| 12 | 4358752 |
| 13 | 12541184 |
| 14 | 35364864 |
| 15 | 97960192 |
| 16 | 267050240 |
| 17 | 717619200 |
| 18 | 1903452160 |
| 19 | 4989337600 |
| 20 | 12937052160 |
| 21 | 33212530688 |
| 22 | 84484882432 |
| 23 | 213090238464 |
| 24 | 533236219904 |