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 | 4 |
| 3 | 15 |
| 4 | 65 |
| 5 | 339 |
| 6 | 2103 |
| 7 | 15171 |
| 8 | 124755 |
| 9 | 1151331 |
| 10 | 11779971 |
| 11 | 132323811 |
| 12 | 1618766691 |
| 13 | 21421525731 |
| 14 | 304887173091 |
| 15 | 4644050174691 |
| 16 | 75378332568291 |
| 17 | 1298783923147491 |
| 18 | 23675771981669091 |
| 19 | 455240918799307491 |