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 | 1 |
| 2 | 6 |
| 3 | 24 |
| 4 | 120 |
| 5 | 460 |
| 6 | 2214 |
| 7 | 8475 |
| 8 | 40164 |
| 9 | 154235 |
| 10 | 724742 |
| 11 | 2792579 |
| 12 | 13050280 |
| 13 | 50432693 |
| 14 | 234766510 |
| 15 | 909442512 |
| 16 | 4221139640 |
| 17 | 16384219216 |
| 18 | 75873259406 |
| 19 | 294977735364 |
| 20 | 1363503281324 |
| 21 | 5308113306398 |
| 22 | 24499364386598 |
| 23 | 95483014454706 |
| 24 | 440147035814920 |
| 25 | 1717035728143720 |
| 26 | 7906666535747934 |