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 | 4 |
| 2 | 26 |
| 3 | 132 |
| 4 | 623 |
| 5 | 2632 |
| 6 | 10500 |
| 7 | 39384 |
| 8 | 141659 |
| 9 | 490100 |
| 10 | 1644186 |
| 11 | 5366436 |
| 12 | 17113433 |
| 13 | 53454528 |
| 14 | 163963312 |
| 15 | 494786352 |
| 16 | 1471423866 |
| 17 | 4318092136 |
| 18 | 12520027756 |
| 19 | 35901819336 |
| 20 | 101909674398 |
| 21 | 286575107424 |
| 22 | 798886300056 |
| 23 | 2209115439664 |
| 24 | 6062818714752 |
| 25 | 16522049256656 |