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.

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.

Links

Table of n, a(n) for n=1..79.

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

Cf. A238984, A239616, A239721, A239722.

Sequence in context: A088759 A227130 A258025 * A195439 A338446 A190719

Adjacent sequences: A239416 A239417 A239418 * A239420 A239421 A239422

Keyword

nonn,base

Author

M. F. Hasler, Aug 01 2014

Status

approved