Challenge!!!

[vbud]

I have posted a similar thread once but no one seemed to have got it right. So here it goes again:

I have a series (Please find some random samples below) of numbers (left) that are generated by a system and their corresponding serials (to the right) which are plain autonumbers. These numbers are passed through the system for a sort of login and and are used only once.
When the number is enterred into the system, a validation is performed which checks if the numbers are correct, i.e if they fit the algo or not and if it has already been used before. The same pattern is used each time for validating. The challenge is to derive which pattern the system uses to generate those numbers and to be able to generate new numbers that will fit the algorithm and therefore allow new logins into the system. Anybody want to give it a try???
Note that the first four numbers are prefixes.

Numbers----------------------------Serials

1372 – 82309 – 63796 -------------- 17982309
1374 – 51171 – 42211 -------------- 18151171
1375 – 78274 – 42416 -------------- 18278274
1377 – 53203 – 41538 -------------- 18453203
1377 – 92076 – 80871 -------------- 18492076
1379 – 61492 – 26299 -------------- 18661492
1379 – 74160 – 99037 -------------- 18674160
1379 – 74167 – 31148 -------------- 18674167
1379 – 74195 – 48088 -------------- 18674195
1379 – 10314 – 10207 -------------- 18610314
1381 – 03451 – 80330 -------------- 18703451
1381 – 33852 – 46359 -------------- 18733852
1382 – 74085 – 35798 -------------- 18874085
1382 – 94057 – 52844 -------------- 18894057
1383 – 42560 – 52041 -------------- 18942560