Strange plus numbers

Strange plus numbers is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

n   is a strange plus number if every adjacent decimal digits are prime sum of its neighbour.

Where     100   <   n   <   500

Ring

<lang ring> load "stdlib.ring"

row = 0 see "Strange plus numbers are:"

for n = 100 to 500

   flag = 1
   str = string(n)
   for m = 1 to len(str)-1
       num1 = number(str[m])
       num2 = number(str[m+1])
       pr = num1+num2
       if not isprime(pr)
          flag = 0
          exit
       ok
    next
    if flag = 1
       row = row + 1
       if (row-1) % 11 = 0
          see nl
       else
          see " " + str
       ok
    ok

next </lang>

Output:

Strange plus numbers are:
 112 114 116 120 121 123 125 129 141 143
 149 161 165 167 202 203 205 207 211 212
 216 230 232 234 238 250 252 256 258 292
 298 302 303 305 307 320 321 323 325 329
 343 347 349 383 385 389 411 412 414 416
 432 434 438 470 474 476 492 494 498