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) |
|---|---|
| 2 | 1 |
| 3 | 9 |
| 4 | 75 |
| 5 | 660 |
| 6 | 6288 |
| 7 | 65051 |
| 8 | 728556 |
| 9 | 8792910 |
| 10 | 113805204 |
| 11 | 1572387410 |
| 12 | 23094192960 |
| 13 | 359209182397 |
| 14 | 5896792771795 |
| 15 | 101854538628396 |
| 16 | 1846058978130172 |
| 17 | 35021271971160507 |
| 18 | 693843099578350329 |
| 19 | 14326635965967487711 |
| 20 | 307729547549467823822 |
| 21 | 6864250658908517748384 |