A117920 Number of digits in the decimal expansion of the regular unit fractions 1/A003592.

1, 2, 1, 3, 1, 4, 2, 2, 5, 3, 2, 6, 4, 2, 3, 7, 5, 3, 3, 8, 6, 4, 3, 9, 4, 7, 5, 3, 10, 4, 8, 6, 4, 11, 4, 9, 5, 7, 5, 12, 4, 10, 5, 8, 6, 13, 4, 11, 5, 9, 6, 7, 14, 5, 12, 5, 10, 6, 8, 15, 6, 13, 5, 11, 6, 9, 16, 7, 7, 14, 5, 12, 6, 10, 17, 7, 8, 15, 6, 13, 6, 11, 18, 7, 9, 16, 8, 7, 14, 6, 12, 19

Offset: 2

Author

Eric W. Weisstein, Apr 02 2006

Keywords

• nonn
• base

Examples

			1/A003592(2) = 1/2 = 0.5, with 1 digit after the decimal point, so a(2) = 1.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 2..10000
• Eric Weisstein's World of Mathematics, Regular Number

Crossrefs

Cf. A003592.

Programs

Mathematica

digNum[n_] := Length[(dig = RealDigits[1/n,10])[[1]]] - dig[[2]]; s = {}; m = 12; Do[n = 5^k; While[n <= 5^m, AppendTo[s, n]; n *= 2], {k, 0, m}]; Rest[digNum /@ Union[s]] (* Amiram Eldar, Feb 08 2020 *)

Extensions

Offset corrected by Amiram Eldar, Feb 08 2020