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 | 20 |
| 4 | 124 |
| 5 | 932 |
| 6 | 8284 |
| 7 | 85220 |
| 8 | 997084 |
| 9 | 13082852 |
| 10 | 190320604 |
| 11 | 3040770020 |
| 12 | 52937870044 |
| 13 | 997533561572 |
| 14 | 20228969244124 |
| 15 | 439283696014820 |
| 16 | 10170742982007004 |
| 17 | 250110224694309092 |
| 18 | 6510327792455418844 |
| 19 | 178832105312143131620 |
| 20 | 5169772417850111583964 |