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) |
|---|---|
| 3 | 2 |
| 4 | 8 |
| 5 | 36 |
| 6 | 140 |
| 7 | 522 |
| 8 | 1920 |
| 9 | 7030 |
| 10 | 25704 |
| 11 | 94302 |
| 12 | 347488 |
| 13 | 1286460 |
| 14 | 4785300 |
| 15 | 17879352 |
| 16 | 67076096 |
| 17 | 252579600 |
| 18 | 954306220 |
| 19 | 3616552422 |
| 20 | 13743371072 |
| 21 | 52356648380 |
| 22 | 199909107900 |
| 23 | 764873459802 |
| 24 | 2932022620160 |
| 25 | 11258982291252 |
| 26 | 43303809016440 |
| 27 | 166799919094902 |
| 28 | 643371241120928 |