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 | 4 |
| 3 | 25 |
| 4 | 176 |
| 5 | 1431 |
| 6 | 12526 |
| 7 | 117850 |
| 8 | 1167446 |
| 9 | 12080563 |
| 10 | 129326575 |
| 11 | 1422908670 |
| 12 | 15999766613 |
| 13 | 183070661566 |
| 14 | 2124252427416 |
| 15 | 24929036429880 |
| 16 | 295250330398281 |
| 17 | 3523043486823439 |
| 18 | 42294807342916249 |
| 19 | 510274778010082846 |
| 20 | 6181011777164665559 |
| 21 | 75112032752942278141 |