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 | 46 |
| 4 | 568 |
| 5 | 9976 |
| 6 | 203104 |
| 7 | 4995136 |
| 8 | 140343808 |
| 9 | 4493656576 |
| 10 | 160609429504 |
| 11 | 6356981099776 |
| 12 | 275688520680448 |
| 13 | 13008983675954176 |
| 14 | 663382602064482304 |
| 15 | 36360098005522825216 |
| 16 | 2131554196360938815488 |
| 17 | 133093201551208236875776 |
| 18 | 8818123347826691244949504 |