A174394 Fourth root of largest n-digit number with exactly five divisors

3, 5, 7, 17, 31, 53, 97, 173, 313, 557, 997, 1777, 3137, 5623, 9973, 17761, 31607, 56209, 99991, 177823, 316223, 562337, 999983, 1778279, 3162277, 5623403, 9999991, 17782769, 31622743, 56234069, 99999989, 177827917, 316227731, 562341293, 999999937, 1778279401, 3162277633, 5623413241, 9999999967, 17782794047, 31622776589, 56234132519, 99999999977, 177827941003, 316227766003, 562341325181, 999999999989, 1778279410013, 3162277660153

Offset

2,1

Links

Table of n, a(n) for n=2..50.

Example

a(2) = 3 since 3^4 = 81, the largest 2-digit number with exactly five divisors (1, 3, 9, 27, 81). All higher 2-digit numbers (82 to 99) have either fewer or more divisors than 81.

Mathematica

Table[Prime[PrimePi[10^(n/4)]], {n, 2, 50}]

Crossrefs

a(n)=(A182647(n))^(1/4).

Sequence in context: A274906 A296422 A370686 * A057476 A016041 A140797

Adjacent sequences: A174391 A174392 A174393 * A174395 A174396 A174397

Keyword

nonn,base

Author

Zak Seidov, Nov 27 2010

Status

approved