A248858 a(n) is number of digits of the smallest term of the sequence A248857 which is of the form 4^n*(5^(2n-1)*10^m-1).

4, 5, 7, 10, 14, 14, 16, 17, 42, 24, 47, 25, 29, 39, 31, 40, 41, 45, 40, 69, 46, 65, 807, 128, 67, 89, 55, 217, 87, 76, 74, 72, 99, 70, 75, 144, 78, 213, 96, 233, 114, 103, 457, 108, 156, 163, 140, 97, 127, 270, 109, 127, 167, 135, 128, 131, 196, 133, 309, 138, 148, 140, 813, 169, 135, 148, 235, 7235

Offset

1,1

Links

Table of n, a(n) for n=1..68.

Example

a(1) = number of digits of 1996 = 4.
a(2) = number of digits of 19984 = 5.
a(3) = number of digits of 1999936 = 7 and
a(68)=7235, because smallest prime of the form 5^(2*68-1)*10^m -1 is 5^135*10^7099-1 and 4^68(5^135*10^7099-1) has 7235 digits.

Crossrefs

Cf. A248857.

Sequence in context: A202342 A234141 A093517 * A145018 A018910 A022936

Adjacent sequences: A248855 A248856 A248857 * A248859 A248860 A248861

Keyword

nonn,base

Author

Farideh Firoozbakht, Jan 06 2015

Status

approved