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) |
|---|---|
| 1 | 0 |
| 2 | 6 |
| 3 | 32 |
| 4 | 222 |
| 5 | 1455 |
| 6 | 9665 |
| 7 | 64047 |
| 8 | 424593 |
| 9 | 2814515 |
| 10 | 18656979 |
| 11 | 123673887 |
| 12 | 819813575 |
| 13 | 5434406883 |
| 14 | 36023773275 |
| 15 | 238795558499 |
| 16 | 1582935756291 |
| 17 | 10493015970771 |
| 18 | 69556445196155 |
| 19 | 461078023878243 |
| 20 | 3056408985571563 |
| 21 | 20260423189286435 |