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A174394 Fourth root of largest n-digit number with exactly five divisors 0
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 (list; graph; refs; listen; history; text; internal format)
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: A002092 A274906 A296422 * A057476 A016041 A140797

Adjacent sequences: A174391 A174392 A174393 * A174395 A174396 A174397

KEYWORD

nonn,base

AUTHOR

Zak Seidov, Nov 27 2010

STATUS

approved

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Last modified December 10 02:09 EST 2022. Contains 358712 sequences. (Running on oeis4.)