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 | 4 |
| 2 | 10 |
| 3 | 30 |
| 4 | 550 |
| 5 | 1540 |
| 6 | 48070 |
| 7 | 223300 |
| 8 | 2634940 |
| 9 | 402610950 |
| 10 | 1570545340 |
| 11 | 13960282700 |
| 12 | 5677137442900 |
| 13 | 248297918605660 |