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%I #15 Dec 20 2021 02:36:50
%S 37,87,137,187,237,287,337,357,367,370,371,372,373,374,375,376,377,
%T 378,379,387,397,437,487,537,587,637,687,735,736,737,738,739,785,786,
%U 787,788,789,837,857,867,870,871,872,873,874,875,876,877,878,879,887,897,937
%N Numbers k such that both k and 2k contain the digit 7.
%e 37 is in the sequence because 2 * 37 = 74, which has one 7.
%e 47 is not in the sequence because 2 * 47 = 94, which has no 7's.
%t Select[Range[10^3], Times @@ Boole@ Map[DigitCount[#, 10, 7] > 0 &, # {1, 2}] > 0 &] (* _Michael De Vlieger_, Apr 26 2017 *)
%Y Cf. A039938.
%K nonn,base
%O 1,1
%A _J. Lowell_, Apr 26 2017
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