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 | 2 |
| 3 | 3 |
| 4 | 18 |
| 5 | 54 |
| 6 | 222 |
| 7 | 779 |
| 8 | 2953 |
| 9 | 10771 |
| 10 | 40043 |
| 11 | 147462 |
| 12 | 545603 |
| 13 | 2013994 |
| 14 | 7442927 |
| 15 | 27490263 |
| 16 | 101563680 |
| 17 | 375176968 |
| 18 | 1386004383 |
| 19 | 5120092320 |
| 20 | 18914660608 |
| 21 | 69873991466 |
| 22 | 258127586367 |
| 23 | 953569519203 |
| 24 | 3522660270539 |