OFFSET
1,1
COMMENTS
Additional rule: If there are fewer than k=4 digits so far, then the sequence is "extended to the left" with the first digit. (It might have been more natural to "extend" with digits 1, i.e., to reduce k to the number of digits if there are less than 4.)
Apart from the trivial cycles (0) and (1) and the cycle (175) considered here, the rule also allows for the "constant" cycle (384), cf. A239722, and (128), cf. A240967.
In general, such "constant" cycles for k=4 (other than the trivial (0) and (1)) must consist of a 3-digit number (100a+10b+c), a,b,c>0, such that a = (10b+c)/(b*c^2-100). The only solutions are: a=1, b=2, c=8; a=1, b=7, c=5; a=3, b=8, c=4. - Bob Selcoe, Aug 04 2014
LINKS
EXAMPLE
For a(1)=53, the sequence is 53,375,315,75,175,175,175,..., since 5*5*5*3 = 375, 3*3*7*5 = 315, 5*3*1*5 = 75, 1*5*7*5 = 175, etc.
PROG
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Aug 01 2014
STATUS
approved