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 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 25 |
| 6 | 90 |
| 7 | 350 |
| 8 | 1701 |
| 9 | 7770 |
| 10 | 42525 |
| 11 | 246730 |
| 12 | 1379400 |
| 13 | 9321312 |
| 14 | 63436373 |
| 15 | 420693273 |
| 16 | 3281882604 |
| 17 | 25708104786 |
| 18 | 197462483400 |
| 19 | 1709751003480 |
| 20 | 15170932662679 |
| 21 | 132511015347084 |
| 22 | 1241963303533920 |
| 23 | 12320068811796900 |
| 24 | 120622574326072500 |
| 25 | 1203163392175387500 |