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A175733
a(n) is the smallest n-digit number with 3 divisors.
6
4, 25, 121, 1369, 10201, 100489, 1018081, 10004569, 100140049, 1000267129, 10000600009, 100008370081, 1000006000009, 10000033772089, 100000380000361, 1000000025191729, 10000001400000049, 100000000621806289, 1000000014000000049, 10000000055856073561
OFFSET
1,1
FORMULA
a(n) = A131581(n-1)^2.
MATHEMATICA
Table[Prime[1 + PrimePi[Sqrt[10^n]]]^2, {n, 0, 25}] (* T. D. Noe, Aug 19 2011 *)
PROG
(Python)
from math import sqrt
from sympy import nextprime
def a(n): return nextprime(int(sqrt(10**n+1)))**2
print([a(n) for n in range(20)]) # Michael S. Branicky, Apr 25 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Aug 24 2010
STATUS
approved