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 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 138 |
| 5 | 1095 |
| 6 | 10208 |
| 7 | 109473 |
| 8 | 1328470 |
| 9 | 18003675 |
| 10 | 269580492 |
| 11 | 4420677525 |
| 12 | 78801184322 |
| 13 | 1517300654415 |
| 14 | 31386251780536 |
| 15 | 694190761402377 |
| 16 | 16348768018619694 |
| 17 | 408472183061464515 |
| 18 | 10791720442056792740 |
| 19 | 300605598797790229629 |
| 20 | 8805117712245004098586 |
| 21 | 270562051319419652165175 |
| 22 | 8702576800277309526639504 |
| 23 | 292425620801795849417200881 |