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A239419
Numbers that end in the trivial cycle (0) under the rule: next term = product of the last three digits of the concatenated preceding terms.
5
0, 3, 5, 7, 8, 10, 15, 16, 17, 20, 25, 30, 33, 35, 36, 40, 41, 45, 50, 51, 52, 53, 54, 55, 56, 58, 59, 60, 61, 63, 65, 67, 70, 74, 75, 76, 77, 78, 79, 80, 84, 85, 88, 89, 90, 95, 97, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 115, 116, 117, 120, 123, 125, 130, 132, 135, 136, 140, 145, 150, 151, 152, 153, 154, 155, 156, 157, 158
OFFSET
1,2
COMMENTS
Additional rule: As long as there are less than k=3 digits in the sequence, the first digit is repeated as often as necessary, e.g. 3 => 3*3*3 = 27 => 3*2*7 = 42 => 7*4*2 = 56 => 2*5*6 = 60 => 6*6*0 = 0 => 6*0*0 => 0, ...
See A238984 for more details, motivation and links.
PROG
(PARI) is_A239419(n) = !A238984(99, n) \\ Here, the somewhat arbitrary value 99 (number of iterations before checking for 0) should be sufficiently large for small n, but might need to be increased for larger starting values n.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Aug 01 2014
STATUS
approved