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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 10 |
| 6 | 15 |
| 7 | 21 |
| 8 | 28 |
| 9 | 36 |
| 10 | 45 |
| 11 | 55 |
| 12 | 65 |
| 13 | 76 |
| 14 | 88 |
| 15 | 101 |
| 16 | 115 |
| 17 | 130 |
| 18 | 146 |
| 19 | 163 |
| 20 | 181 |
| 21 | 200 |
| 22 | 220 |
| 23 | 240 |
| 24 | 261 |
| 25 | 283 |
| 26 | 306 |
| 27 | 330 |
| 28 | 355 |
| 29 | 381 |
| 30 | 408 |
| 31 | 436 |
| 32 | 465 |
| 33 | 495 |
| 34 | 525 |
| 35 | 556 |
| 36 | 588 |
| 37 | 621 |
| 38 | 655 |
| 39 | 690 |
| 40 | 726 |
| 41 | 763 |
| 42 | 801 |
| 43 | 840 |
| 44 | 880 |
| 45 | 920 |
| 46 | 961 |
| 47 | 1003 |
| 48 | 1046 |
| 49 | 1090 |
| 50 | 1135 |
| 51 | 1181 |
| 52 | 1228 |
| 53 | 1276 |
[0,0,1,3,6,10,15,21,28,36,45,55,65,76,88,101,115, 130,146,163,181,200,220,240,261,283,306,330,355, 381,408,436,465,495,525,556,588,621,655,690,726, 763,801,840,880,920,961,1003,1046,1090,1135,1181, 1228,1276] |