A285803 Numbers k such that both k and 2k contain the digit 7.
37, 87, 137, 187, 237, 287, 337, 357, 367, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 387, 397, 437, 487, 537, 587, 637, 687, 735, 736, 737, 738, 739, 785, 786, 787, 788, 789, 837, 857, 867, 870, 871, 872, 873, 874, 875, 876, 877, 878, 879, 887, 897, 937
Offset: 1
Examples
37 is in the sequence because 2 * 37 = 74, which has one 7. 47 is not in the sequence because 2 * 47 = 94, which has no 7's.
Crossrefs
Cf. A039938.
Programs
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Mathematica
Select[Range[10^3], Times @@ Boole@ Map[DigitCount[#, 10, 7] > 0 &, # {1, 2}] > 0 &] (* Michael De Vlieger, Apr 26 2017 *)