Copyright 2004 Ray Ontko & Co.  All rights reserved.

begin-program
input $answer 'Which element in the sequence'
move $answer to #answer
do f(#answer,#result)
show #result edit 999999
end-program

begin-procedure f(#param, :#return)
if #param < 2
   move 1 to #return
else
   subtract 1 from #param
   do f(#param, #tmp1)
   subtract 1 from #param
   do f(#param, #tmp2)
   let #return = #tmp1 + #tmp2
end-if
end-procedure f