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 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 22 |
| 6 | 202 |
| 7 | 1854 |
| 8 | 17866 |
| 9 | 183806 |
| 10 | 2029850 |
| 11 | 24081006 |
| 12 | 306486314 |
| 13 | 4175102110 |
| 14 | 60708557626 |
| 15 | 939518187726 |
| 16 | 15430666746826 |
| 17 | 268214861561726 |
| 18 | 4921023843969242 |
| 19 | 95066628485598126 |
| 20 | 1929291834938927210 |
| 21 | 41042364285004263262 |
| 22 | 913409469123533445754 |
| 23 | 21227246586149632119438 |