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 | 5 |
| 3 | 20 |
| 4 | 85 |
| 5 | 400 |
| 6 | 2046 |
| 7 | 11226 |
| 8 | 65676 |
| 9 | 407787 |
| 10 | 2675410 |
| 11 | 18475311 |
| 12 | 133843405 |
| 13 | 1014271763 |
| 14 | 8019687099 |
| 15 | 66011609670 |
| 16 | 564494701167 |
| 17 | 5005880952390 |
| 18 | 45958055208576 |
| 19 | 436161412834300 |
| 20 | 4273045478169842 |
| 21 | 43160044390231165 |