A039938 Smallest k for which k, 2k, ... nk all contain the digit 7.

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

Author

Erich Friedman

Keywords

• base
• nonn

Examples

			a(2)=37 since 37 and 74 contain a 7.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..125

Crossrefs

Cf. A039932, A039933, A039934, A039935, A039936, A039937, A039939, A039940.

Programs

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 *)

Extensions

More terms from Patrick De Geest, Oct 15 1999