In how many positive four-digit integers that are not multiples of 1111 do the digits form an arithmetic sequence?
If I understand your question:
All 4-digit integers beginning with 1,000, 1001, 1002......etc. form an AS till you reach 1,111. Then the AS continues at 1,112, 1,113, 1,114....etc. until you reach 2,222. Then it keeps going from 2,223, 2,224, 2,225 until you reach 3333.......and so on until your reach 9,998.
The total number of 4-digit integers that form arithmetic sequences would be:
9000 - 9 =8,991 such numbers.
