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A325440
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a(n) is the least number not 2*a(m)-1 or 3*a(m)-1 for any m < n.
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4
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1, 3, 4, 6, 9, 10, 12, 13, 14, 15, 16, 18, 20, 21, 22, 24, 28, 30, 32, 33, 34, 36, 37, 40, 42, 45, 46, 48, 49, 50, 51, 52, 54, 56, 57, 58, 60, 61, 64, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 92, 93, 94, 96, 100, 102, 104
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OFFSET
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1,2
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LINKS
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EXAMPLE
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The sequence necessarily starts with 1. The next 2 terms are determined as follows: because a(1) = 1, the number 2 is disallowed, so that a(2) = 3, whence the numbers 5 and 8 are disallowed, and a(3) = 4. See A325417 for a guide to related sequences.
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MATHEMATICA
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a = {1}; Do[AppendTo[a, NestWhile[# + 1 &, Last[a] + 1, Apply[Or,
Map[MemberQ[a, #] &, Select[Flatten[{(#+1)/2, (#+1)/3}],
IntegerQ]]] &]], {150}]; a (* A325440 *)
Complement[Range[Last[a]], a] (* A325441 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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