python中的三角形数字

在Python中，三角形数字是指一个数字在三角形数字序列中的位置。三角形数字序列是一个数学序列，其中每个数字都是它上面两个数字的和。例如，三角形数字序列的前几个数字是：1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435, 465, 506, 540, 575, 611, 650, 690, 731, 773, 816, 860, 905, 951, 998, 1046, 1105, 1165, 1226, 1289, 1353, 1419, 1486, 1554, 1623, 1693, 1764, 1836, 1910, 1985, 2061, 2140, 2220, 2301, 2383, 2466, 2550, 2635, 2721, 2808, 2906, 3005, 3105, 3206, 3309, 3413, 3519, 3626, 3734, 3843, 3953, 4064, 4176, 4290, 4405, 4521, 4638, 4757, 4877, 4998, 5119, 5242, 5366, 5491, 5617, 5744, 5873, 6003, 6134, 6266, 6400, 6535, 6672, 6810, 6950, 7091, 7233, 7376, 7520, 7665, 7811, 7958, 8106, 8255, 8405, 8557, 8710, 8864, 9020, 9177, 9335, 9504, 9674, 9845, 10017, 10191, 10366, 10543, 10721, 10901, 11082, 11264, 11447, 11632, 11818, 12005, 12203, 12402, 12602, 12803, 13005, 13208, 13412, 13617, 13823, 14030, 14238, 14447, 14657, 14868, 15081, 15295, 15510, 15726, 15943, 16161, 16380, 16600, 16821, 17043, 17266, 17490, 17715, 17941, 18168, 18396, 18625, 18855, 19086, 19318, 19551, 19785, 20019, 20254, 20490, 20727, 20965, 21204, 21444, 21685, 21927, 22169, 22412, 22656, 22901, 23147, 23394, 23642, 23891, 24141, 24392, 24644, 24900, 25157, 25415, 25675, 25936, 26198, 26461, 26725, 26990, 27256, 27523, 27791, 28060, 28329, 28599, 28870, 29142, 29415, 29688, 29962, 30237, 30513, 30790, 31068, 31347, 31627, 31908, 32190, 32473, 32757, 33042, 33328, 33615, 33903, 34192, 34481, 34771, 35061, 35352, 35644, 35937, 36231, 36526, 36822, 37119, 37417, 37716, 38016, 38317, 38619, 38922, 39226, 39531, 39837, 40144, 40452, 40761, 41071, 41382, 417