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 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 40 |
| 4 | 360 |
| 5 | 3570 |
| 6 | 37476 |
| 7 | 410490 |
| 8 | 4635330 |
| 9 | 53589045 |
| 10 | 631115140 |
| 11 | 7544876956 |
| 12 | 91321148575 |
| 13 | 1116879203135 |
| 14 | 13781214640630 |
| 15 | 171350293212360 |
| 16 | 2144719821588471 |
| 17 | 27001925967762160 |
| 18 | 341717698703959875 |