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 | 12 |
| 4 | 65 |
| 5 | 440 |
| 6 | 3571 |
| 7 | 33824 |
| 8 | 366113 |
| 9 | 4458240 |
| 10 | 60321091 |
| 11 | 897774592 |
| 12 | 14576528801 |
| 13 | 256391130112 |
| 14 | 4856647308787 |
| 15 | 98567413125120 |
| 16 | 2133825372539585 |
| 17 | 49080991762153472 |
| 18 | 1195339768057071619 |
| 19 | 30729146849826701312 |
| 20 | 831545527540481198465 |
| 21 | 23627123985544955559936 |