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 | 5 |
| 2 | 20 |
| 3 | 80 |
| 4 | 300 |
| 5 | 1140 |
| 6 | 4260 |
| 7 | 15960 |
| 8 | 59580 |
| 9 | 222600 |
| 10 | 830880 |
| 11 | 3102120 |
| 12 | 11578800 |
| 13 | 43220940 |
| 14 | 161324400 |
| 15 | 602159940 |
| 16 | 2247585300 |
| 17 | 8389237320 |
| 18 | 31313155560 |
| 19 | 116877700500 |
| 20 | 436250537520 |