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 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 90 |
| 5 | 540 |
| 6 | 3276 |
| 7 | 21021 |
| 8 | 137445 |
| 9 | 916300 |
| 10 | 6167700 |
| 11 | 41812200 |
| 12 | 284604840 |
| 13 | 1942428033 |
| 14 | 13278352815 |
| 15 | 90862598190 |
| 16 | 622150990734 |
| 17 | 4261620339460 |
| 18 | 29198279495220 |
| 19 | 200080147593645 |
| 20 | 1371167039301345 |
| 21 | 9397260307853496 |
| 22 | 64406143791454248 |
| 23 | 441430873666787088 |
| 24 | 3025546968019741200 |