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 | 15 |
| 3 | 57 |
| 4 | 215 |
| 5 | 812 |
| 6 | 3083 |
| 7 | 11750 |
| 8 | 44934 |
| 9 | 172401 |
| 10 | 663370 |
| 11 | 2559008 |
| 12 | 9894006 |
| 13 | 38331115 |
| 14 | 148770379 |
| 15 | 578346672 |
| 16 | 2251636041 |
| 17 | 8777816518 |
| 18 | 34261079538 |
| 19 | 133873978089 |
| 20 | 523638632149 |
| 21 | 2050085911219 |
| 22 | 8033148700174 |
| 23 | 31502487793694 |