A070021 1/n has period 1 in base 10 (but not terminating).

3, 6, 9, 12, 15, 18, 24, 30, 36, 45, 48, 60, 72, 75, 90, 96, 120, 144, 150, 180, 192, 225, 240, 288, 300, 360, 375, 384, 450, 480, 576, 600, 720, 750, 768, 900, 960, 1125, 1152, 1200, 1440, 1500, 1536, 1800, 1875, 1920, 2250, 2304, 2400, 2880, 3000, 3072, 3600

Offset: 1

Author

Henry Bottomley, Apr 12 2002

Keywords

• nonn
• base
• easy

Examples

			12 is in the sequence since 1/12=0.08333333333...; 11 is not since 1/11=0.0909090909...; 10 is not, since despite 1/10=0.099999999..., it is also true that 1/10=0.1 exactly.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..11778 (a(n) < 10^50)

Crossrefs

Cf. A003592, A069105, A070022, A070023.

Programs

Mathematica

mx = 5000; Select[ Union@ Flatten@ Table[2^t*5^f {3, 9}, {t, 0, Log[2, mx/3]}, {f, 0, Log[5, mx/(2^t*3)]}], # < mx &] (* Robert G. Wilson v, Apr 27 2017 *)

Formula

Numbers of the form a*b*c where a is in {3, 9}, b is a power of 2 and c is a power of 5.