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 | -2 |
| 2 | 6 |
| 3 | -14 |
| 4 | 54 |
| 5 | -62 |
| 6 | 966 |
| 7 | 4786 |
| 8 | 71574 |
| 9 | 875938 |
| 10 | 12810726 |
| 11 | 202739986 |
| 12 | 3511712694 |
| 13 | 65856494338 |
| 14 | 1330170266886 |
| 15 | 28785391689586 |
| 16 | 664456856787414 |
| 17 | 16296345814039138 |
| 18 | 423191833100881446 |
| 19 | 11600198414334789586 |
| 20 | 334710974532291679734 |
| 21 | 10140603124807778534338 |