What are the missing numbers in this sequence:
0, __, 2, __, 9, __, 20, __, 26, __, 54, __, 77, __

let S(n) equal the sum of the co-primes of n that are less than n.  Then the sequence is given by

S(1)=0, S(2)=0, S(3)=2 and so on.  Thus the complete series is

 

0,0,2,3,9,5,20,15,26,19,54,23,77,41

Posted by Daniel on 2007-08-22 01:18:49