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 | 9 |
| 3 | 45 |
| 4 | 165 |
| 5 | 495 |
| 6 | 1287 |
| 7 | 3003 |
| 8 | 6435 |
| 9 | 12870 |
| 10 | 24309 |
| 11 | 43741 |
| 12 | 75465 |
| 13 | 125445 |
| 14 | 201675 |
| 15 | 314523 |
| 16 | 477015 |
| 17 | 705012 |
| 18 | 1017225 |
| 19 | 1435005 |
| 20 | 1981845 |
| 21 | 2682559 |
| 22 | 3562131 |
| 23 | 4644255 |
| 24 | 5949615 |
| 25 | 7493982 |
| 26 | 9286233 |
| 27 | 11326425 |
| 28 | 13604085 |
| 29 | 16096905 |
| 30 | 18770031 |
| 31 | 21576079 |
| 32 | 24455955 |
| 33 | 27340500 |
| 34 | 30152925 |
| 35 | 32811945 |
| 36 | 35235465 |
| 37 | 37344615 |
| 38 | 39067875 |
| 39 | 40344975 |
| 40 | 41130255 |
| 41 | 41395240 |
| 42 | 41130255 |
| 43 | 40344975 |
| 44 | 39067875 |
| 45 | 37344615 |
| 46 | 35235465 |
| 47 | 32811945 |
| 48 | 30152925 |
| 49 | 27340500 |
| 50 | 24455955 |
| 51 | 21576079 |
| 52 | 18770031 |
| 53 | 16096905 |
| 54 | 13604085 |
| 55 | 11326425 |
| 56 | 9286233 |
| 57 | 7493982 |
| 58 | 5949615 |
| 59 | 4644255 |
| 60 | 3562131 |
| 61 | 2682559 |
| 62 | 1981845 |
| 63 | 1435005 |
| 64 | 1017225 |
| 65 | 705012 |
| 66 | 477015 |
| 67 | 314523 |
| 68 | 201675 |
| 69 | 125445 |
| 70 | 75465 |
| 71 | 43741 |
| 72 | 24309 |
| 73 | 12870 |
| 74 | 6432 |
| 75 | 3003 |
| 76 | 1287 |
| 77 | 495 |
| 78 | 165 |
| 79 | 45 |
| 80 | 9 |
| 81 | 1 |