The sequence is the 1st prime, the 3rd prime, the 5th prime, etc., i.e. every other prime. The only language I know is LibertyBasic. Here is the program in that language. The ' indicates a comment line. -------------------------------------------------------------------------- 'We begin by printing the first term. The only term that's even. 'and setting the prime count = 1 print 2;" "; count = 1 'Now we need try only odd numbers n from 5 to 100. That's why the 'step 2" in the next executable line. If we want numbers higher 'than 100, then we change the 100 to a higher number. for n = 3 to 100 step 2 pr = 1 'We test each n to see if it is prime. We use 1 or 0 'values of "pr" to indicate whether n is prime or not 'if pr=1 it is prime, and if pr=0 it is not prime 'We started above by setting pr=1, for we change pr to 0 'if n is not prime. Since n is odd, we only 'need to see if n is divisible by odd numbers, 'which is why the "step 2" in the next line. for k = 3 to n-1 step 2 'the next line makes pr=0 if n is divisible by k if n mod k = 0 then pr=0 next k 'if n is not prime the next line skips to 1 for the next n value if pr = 0 then 1 'if n is prime, we increase the prime count by 1 count = count+1 'the next line determines whether the count is even or 'odd. If it's odd, we print n; if even we skip to 1 if count mod 2 = 0 then 1 print n;" "; 1 next n print "..." ----------------------------------------- Edwin