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 | 4 |
| 2 | 19 |
| 3 | 104 |
| 4 | 641 |
| 5 | 4364 |
| 6 | 32251 |
| 7 | 254176 |
| 8 | 2091841 |
| 9 | 17435924 |
| 10 | 138844931 |
| 11 | 891248984 |
| 12 | 263059969 |
| 13 | -163754125796 |
| 14 | -4970760027029 |
| 15 | -117798281164336 |
| 16 | -2588474951884159 |
| 17 | -55489648295242204 |
| 18 | -1184521077396558989 |
| 19 | -25406942370946446776 |
| 20 | -549455868757454486399 |
| 21 | -11980725887273702949076 |