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 | 0 |
| 3 | 1 |
| 4 | 8 |
| 5 | 45 |
| 6 | 242 |
| 7 | 1414 |
| 8 | 9432 |
| 9 | 72246 |
| 10 | 628260 |
| 11 | 6116319 |
| 12 | 65856928 |
| 13 | 776628203 |
| 14 | 9950798214 |
| 15 | 137612550620 |
| 16 | 2042588039056 |
| 17 | 32384583304092 |
| 18 | 546155914771464 |
| 19 | 9761655297881037 |
| 20 | 184309987662192600 |
| 21 | 3665514979650544153 |
| 22 | 76586509823743735706 |
| 23 | 1677182881414143407490 |