In the sequence 1, 9, 7, 7, 4, 7, 5, 3, 9, 4, 1, . . ., every digit from the fifth on
is the sum of the preceding digits mod 10. Does one of the following words ever
occur in the sequence.
(a) 1234 (b) 3269 (c) 1977 (d) 0197?
Please give me a detailed explanation as I did not understand the one from Arthur engel
.
.