The numbers are just the sum of digits of the primes. 1+1=2 1+3=4 1+7=8 1+9=10 2+3=5 2+9=11
My first solution is equivalent but more complicated: each prime minus 9 times its tens digit. Although I made the error of considering 27 prime instead of 29.
re(2): Not sure why you would do this... (Probable intended solution.)
