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 | 18 |
| 4 | 157 |
| 5 | 1776 |
| 6 | 24807 |
| 7 | 413344 |
| 8 | 8004537 |
| 9 | 176630400 |
| 10 | 4374300331 |
| 11 | 120136735104 |
| 12 | 3623854678677 |
| 13 | 119102912981248 |
| 14 | 4236492477409935 |
| 15 | 162152320065532416 |
| 16 | 6645233337842716273 |
| 17 | 290321208589666369536 |
| 18 | 13469914225467040015827 |
| 19 | 661442143465113960448000 |