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 | 3 |
| 3 | 7 |
| 4 | 61 |
| 5 | 261 |
| 6 | 3991 |
| 7 | 24403 |
| 8 | 524217 |
| 9 | 4149001 |
| 10 | 114544171 |
| 11 | 1111976031 |
| 12 | 37492210933 |
| 13 | 431097055117 |
| 14 | 17165526306111 |
| 15 | 228085258466731 |
| 16 | 10472666396599921 |
| 17 | 157882659583461393 |
| 18 | 8211536252680154707 |
| 19 | 138474928851961700791 |
| 20 | 8045878340298511456941 |