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 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 75 |
| 5 | 540 |
| 6 | 4670 |
| 7 | 47110 |
| 8 | 543130 |
| 9 | 7044450 |
| 10 | 101519250 |
| 11 | 1609319250 |
| 12 | 27830729850 |
| 13 | 521397676800 |
| 14 | 10519576867800 |
| 15 | 227400111939000 |
| 16 | 5243385642495000 |
| 17 | 128458209887007000 |
| 18 | 3332234177825553000 |
| 19 | 91241046790816923000 |
| 20 | 2629791992312269785000 |