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 | 1 |
| 2 | 1 |
| 3 | 13 |
| 4 | 49 |
| 5 | 241 |
| 6 | 2401 |
| 7 | 13021 |
| 8 | 128353 |
| 9 | 1346689 |
| 10 | 10615681 |
| 11 | 140431501 |
| 12 | 1544877841 |
| 13 | 17576665393 |
| 14 | 264566466529 |
| 15 | 3226728670621 |
| 16 | 48376006929601 |
| 17 | 766753039205761 |
| 18 | 11052669865900033 |
| 19 | 197019825098096269 |
| 20 | 3271213100827557361 |
| 21 | 56597110823949654001 |