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A039938
Smallest k for which k, 2k, ... nk all contain the digit 7.
12
7, 37, 237, 1789, 4357, 14379, 19587, 93957, 189572, 189572, 189597, 189597, 189597, 1234397, 1839597, 1958798, 1983957, 1983957, 1983957, 1983957, 1983957, 1983957, 3978594, 11983957, 19596487, 29195397, 29195397, 29195397
OFFSET
1,1
LINKS
EXAMPLE
a(2)=37 since 37 and 74 contain a 7.
MATHEMATICA
Table[SelectFirst[Range[10^6], Times @@ Boole@ Map[DigitCount[#, 10, 7] > 0 &, # Range@ n] > 0 &], {n, 12}] (* Michael De Vlieger, Apr 27 2017, Version 10 *)
KEYWORD
base,nonn
EXTENSIONS
More terms from Patrick De Geest, Oct 15 1999
STATUS
approved