[seqfan] Re: Numbers with 3 divisors

[Harvey P. Dale]

	Thanks to Chris and Ant for this (in retrospect fairly obvious)
insight, one which however I didn't perceive on my own.  I have
submitted a program to generate the terms of A175734, using their
insight, that is many thousands of times as fast as the
brute-force-method program that I ran last night.

	Best,
	Harvey
 

-----Original Message-----
From: seqfan-bounces at list.seqfan.eu
[mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Christopher Gribble 
Sent: Thursday, August 18, 2011 8:02 AM
To: 'Sequence Fanatics Discussion list'
Subject: [seqfan] Re: Numbers with 3 divisors

A number with exactly 3 divisors can only be the square of a prime.
Apart from primes 2 and 5, all other primes end in 1, 3, 7 or 9, so
their
squares end in 1 or 9.

Best regards,

Chris Gribble


-----Original Message-----
From: seqfan-bounces at list.seqfan.eu
[mailto:seqfan-bounces at list.seqfan.eu]
On Behalf Of Harvey P. Dale
Sent: 18 August 2011 12:42 PM
To: seqfan at seqfan.eu
Subject: [seqfan] Numbers with 3 divisors

            Is it true that all numbers with exactly three divisors,
with
the exception only of 4 and 25, have either 1 or 9 as their last decimal
digit?

            Best,

            Harvey


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