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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 29 |
| 5 | 140 |
| 6 | 757 |
| 7 | 4858 |
| 8 | 36409 |
| 9 | 302520 |
| 10 | 2681769 |
| 11 | 25018510 |
| 12 | 245905365 |
| 13 | 2559272196 |
| 14 | 28264854685 |
| 15 | 330408571202 |
| 16 | 4065526003313 |
| 17 | 52349977261040 |
| 18 | 702393407898705 |
| 19 | 9795673312888214 |
| 20 | 141820637175889805 |