A175733 - OEIS

A175733

a(n) is the smallest n-digit number with 3 divisors.

4, 25, 121, 1369, 10201, 100489, 1018081, 10004569, 100140049, 1000267129, 10000600009, 100008370081, 1000006000009, 10000033772089, 100000380000361, 1000000025191729, 10000001400000049, 100000000621806289, 1000000014000000049, 10000000055856073561

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

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

Cf. A131581, A132153, A136582, A175734.

Sequence in context: A013582 A260373 A362391 * A240479 A317949 A263440

Adjacent sequences: A175730 A175731 A175732 * A175734 A175735 A175736

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Aug 24 2010

STATUS

approved