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 | 3 |
| 4 | 12 |
| 5 | 70 |
| 6 | 465 |
| 7 | 3591 |
| 8 | 31948 |
| 9 | 319068 |
| 10 | 3539385 |
| 11 | 43205635 |
| 12 | 575312826 |
| 13 | 8298867798 |
| 14 | 128921967265 |
| 15 | 2145837600375 |
| 16 | 38097353658120 |
| 17 | 718657756980376 |
| 18 | 14354000800751313 |
| 19 | 302625047150614179 |
| 20 | 6716038666999745710 |
| 21 | 156498725047355717250 |
| 22 | 3820426102008414736761 |