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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 88 |
| 6 | 303 |
| 7 | 1033 |
| 8 | 3544 |
| 9 | 12220 |
| 10 | 42164 |
| 11 | 145364 |
| 12 | 500954 |
| 13 | 1726408 |
| 14 | 5950050 |
| 15 | 20507364 |
| 16 | 70680192 |
| 17 | 243602952 |
| 18 | 839588620 |
| 19 | 2893682172 |
| 20 | 9973219220 |
| 21 | 34373198420 |
| 22 | 118468937648 |
| 23 | 408309065104 |
| 24 | 1407257423576 |
| 25 | 4850182474912 |