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 | 3 |
| 1 | 9 |
| 2 | 30 |
| 3 | 102 |
| 4 | 352 |
| 5 | 1230 |
| 6 | 4344 |
| 7 | 15483 |
| 8 | 55626 |
| 9 | 201246 |
| 10 | 732564 |
| 11 | 2681223 |
| 12 | 9861342 |
| 13 | 36428320 |
| 14 | 135100620 |
| 15 | 502841295 |
| 16 | 1877678370 |
| 17 | 7032454470 |
| 18 | 26410804020 |
| 19 | 99437742720 |
| 20 | 375260126904 |
| 21 | 1419223506516 |
| 22 | 5378236459328 |
| 23 | 20419260060462 |
| 24 | 77659985060772 |
| 25 | 295844249258796 |
| 26 | 1128738495397128 |
| 27 | 4312685074680465 |
| 28 | 16500218817839274 |
| 29 | 63209983347693924 |