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A165305
a(n) is the smallest number not yet in the sequence such that the concatenation of all terms yields a periodic stream of digits 1, 2, 3, ..., 7 (repeat from 1).
3
1, 2, 3, 4, 5, 6, 7, 12, 34, 56, 71, 23, 45, 67, 123, 456, 712, 345, 671, 234, 567, 1234, 5671, 2345, 6712, 3456, 7123, 4567, 12345, 67123, 45671, 23456, 71234, 56712, 34567, 123456, 712345, 671234, 567123, 456712, 345671, 234567, 1234567
OFFSET
1,2
EXAMPLE
For a(8), having already 1, 2, 3, 4, 5, 6, 7, the next number must be 12 because after 1,2,3,4,5,6,7 we shall continue with a 1.
But 1 is already in the sequence so we need to add a 2 -> 12. And so on.
CROSSREFS
KEYWORD
easy,base,nonn
AUTHOR
EXTENSIONS
Keyword base added by R. J. Mathar, Feb 02 2010
STATUS
approved