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 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 23 |
| 4 | 120 |
| 5 | 629 |
| 6 | 3260 |
| 7 | 16843 |
| 8 | 86832 |
| 9 | 447241 |
| 10 | 2302516 |
| 11 | 11851487 |
| 12 | 60995880 |
| 13 | 313912637 |
| 14 | 1615504748 |
| 15 | 8313878227 |
| 16 | 42785563488 |
| 17 | 220186165393 |
| 18 | 1133137017700 |
| 19 | 5831424517415 |
| 20 | 30010056528600 |
| 21 | 154439694647429 |
| 22 | 794787521046812 |
| 23 | 4090186754982235 |
| 24 | 21049182488180880 |