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 | 4 |
| 4 | 17 |
| 5 | 141 |
| 6 | 1297 |
| 7 | 17683 |
| 8 | 262145 |
| 9 | 4861405 |
| 10 | 100112001 |
| 11 | 2371816701 |
| 12 | 61917364225 |
| 13 | 1796326510993 |
| 14 | 56693912375297 |
| 15 | 1947734359001551 |
| 16 | 72059082110369793 |
| 17 | 2863257607266475419 |
| 18 | 121439531096594251777 |
| 19 | 5480987217944109919765 |
| 20 | 262144000000000000000001 |