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arithmetic n.  and  practical n.

First numbers that belong to both sets:

1, 6, 20, 30, 42, 54, 56, 60, 66, 78, 96, 126, 132, 140, 150, 168, 198, 204, 210, 220, 224, 260, 264, 270, 276, 280, 294, 304, 308, 330, 340, 342, 348, 352, 378, 380, 390, 414, 420, 432, 456, 460, 462, 464, 476, 480, 486, 500, 504, 510, 540, 546, 552, 558, 570, 580, 594, 608, 612, 616, 620, 630, 644, 660, 672, 690, 702, 714, 726, 728, 736, 740, 744, 750, 780, 798, 812, 820, 832, 840, 858, 860, 864, 870, 912, 918, 920, 924, 930, 952, 966, 980, 990, 992, 1014, 1020, 1026, 1032, 1050, 1056, 1064, 1110, 1120, 1122, 1128, 1140, 1148, 1188, 1218, 1230, 1240, 1242, 1248, 1254, 1288, 1290, 1302, 1316, 1320, 1326, 1350, 1376, 1380, 1386, 1392, 1400, 1410, 1416, 1428, 1470, 1482, 1484, 1500, 1504, 1512, 1518, 1520, 1540, 1554, 1566, 1590, 1624, 1632, 1638, 1650, 1656, 1672, 1674, 1700, 1710, 1716, 1722, 1736, 1740, 1760, 1770, 1794, 1806, 1820, 1824, 1830, 1836, 1848, 1860, 1880, 1888, 1890, 1908, 1914, 1932, 1950, 1974, 1980, 1998, 2010, 2016, 2024, 2046, 2058, 2070, 2072, 2128, 2130, 2142, 2156, 2160, 2184, 2190, 2208, 2214, 2220, 2226, 2232, 2244, 2262, 2280, 2296, 2310, 2320, 2322, 2376, 2380, 2392, 2394, 2400, 2408, 2418, 2430, 2436, 2442, 2460, 2464, 2478, 2484, 2496, 2508, 2520, 2538, 2550, 2556, 2562, 2574, 2580, 2624, 2632, 2646, 2652, 2660, 2688, 2706, 2728, 2730, 2744, 2760, 2784, 2790, 2814, 2820, 2832, 2838, 2840, 2850, 2856, 2860, 2862, 2886, 2898, 2912, 2940, 2968, 2970, 2976, 2982, 3024, 3036, 3040, 3060, 3066, 3078, 3080, 3102, 3132, 3160, 3168, 3180, 3186, 3192, 3198, 3204, 3220, 3224, 3234, 3248, 3294, 3304, 3318, 3332, 3344, 3354, 3360.

Some larger examples :