Asked by Lola

In how many positive four-digit integers that are not multiples of 1111 do the digits form an arithmetic sequence? (The digits must form an arithmetic sequence, in order. For example, the number 5137 does not count.)
Answered by Steve
so, start with 1xxx. With various values of d, we get
d=1: 1234, 2345, 3456, 4567, 5678, 6789
d=2: 1357, 2468, 3579
d=3: 147? bzzt

Now, with negative d, we have
d=-1: 9876, 8765, 7654, 6543, 5432, 4321, 3210
d=-2: 9753, 8642, 7531, 6420
d=-3: 9630

So, of the numbers listed, how many are not multiples of 1111?
Answered by Anonamous
6+7+4+1+3=21
Answered by YEET
STEVE YOU MSUT HAVE POOP FOR BRAINS!
Answered by Agree
Agree that the answer is 21
Answered by August Mittag
Yes, I checked. The answer is 21.