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A282169
a(n) is the minimal product of a positive integer sequence of length n with no duplicate substrings of length greater than 1, and every number different from its neighbors.
4
1, 2, 2, 6, 6, 24, 24, 120, 120, 576, 720
OFFSET
1,2
COMMENTS
Examples:
[1,1] is not a valid sequence because 1 is self-adjacent.
[1,2,3,1,2] is not valid because the substring [1,2] appears twice.
EXAMPLE
a(1) = 1 via [1];
a(2) = 2 via [1,2];
a(3) = 2 via [1,2,1];
a(4) = 6 via [1,2,1,3];
a(5) = 6 via [1,2,1,3,1];
a(6) = 24 via [1,2,1,3,1,4];
a(7) = 24 via [1,2,1,3,1,4,1];
a(8) = 120 via [1,2,1,3,1,4,1,5];
a(9) = 120 via [1,2,1,3,1,4,1,5,1];
a(10) = 576 via [1,2,1,3,1,4,2,3,4,1];
a(11) = 720 via [1,2,1,3,1,4,1,5,1,6,1].
CROSSREFS
Cf. A282164.
Cf. A282166 is the sum analog.
Sequence in context: A135401 A129881 A132369 * A081123 A056038 A076929
KEYWORD
nonn,more
AUTHOR
Peter Kagey, Feb 07 2017
STATUS
approved