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 | 4 |
| 2 | 9 |
| 3 | 25 |
| 4 | 75 |
| 5 | 229 |
| 6 | 699 |
| 7 | 2125 |
| 8 | 6435 |
| 9 | 19429 |
| 10 | 58539 |
| 11 | 176125 |
| 12 | 529395 |
| 13 | 1590229 |
| 14 | 4774779 |
| 15 | 14332525 |
| 16 | 43013955 |
| 17 | 129074629 |
| 18 | 387289419 |
| 19 | 1161999325 |
| 20 | 3486260115 |
| 21 | 10459304629 |
| 22 | 31378962459 |
| 23 | 94138984525 |
| 24 | 282421147875 |
| 25 | 847271832229 |
| 26 | 2541832273899 |
| 27 | 7625530376125 |
| 28 | 22876658237235 |
| 29 | 68630108929429 |
| 30 | 205890595223739 |