
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
April 11th, 2017, 01:15 AM  #1 
Newbie Joined: Apr 2016 From: England Posts: 13 Thanks: 2  Working out numbers which are in both sequences.
This question's really stumped me, and I can't seem to find any tutorials on how to answer it... The nth term of a sequence is 2n + 1 The nth term of a different sequence is 3n 1 Work out the three numbers that are in both sequences and between 20 and 40 Now the three numbers I managed to get are 25, 31 and 37 (as I assumed it meant the output of both of these sequences needs to be the same as well as being in between 20 and 40). For example 2x18+1= 37 as does 3x12+1= 37. Yet I still feel I'm going the wrong way around this. Many thanks in advance Last edited by skipjack; April 11th, 2017 at 03:05 AM. 
April 11th, 2017, 01:45 AM  #2  
Senior Member Joined: Sep 2015 From: Southern California, USA Posts: 1,410 Thanks: 715  Quote:
$3n+1$ will be odd for $n$ even the numbers with even index in the 2nd sequence between 20 and 40 are 25,31,37 as you discovered. Last edited by skipjack; April 11th, 2017 at 03:06 AM.  

Tags 
numbers, sequences, working 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Working with 'special' Numbers  Martin Hopf  Number Theory  17  April 4th, 2015 04:13 PM 
sequences of natural numbers whose sum is n  wilhelm  Number Theory  5  November 30th, 2012 09:23 AM 
Sequences and imaginary numbers  doctorbleachers  Algebra  1  May 22nd, 2012 12:35 PM 
Digits and sequences of prime numbers  momo  Number Theory  19  November 22nd, 2007 09:28 AM 
sequences of natural numbers whose sum is n  wilhelm  Applied Math  0  December 31st, 1969 04:00 PM 