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A077477
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Least positive integers not excluded by the rule that if n is present then 2n+1 and 3n+1 are not allowed.
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6
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1, 2, 6, 8, 9, 10, 11, 12, 14, 15, 16, 18, 20, 22, 24, 26, 27, 30, 32, 35, 36, 38, 39, 40, 42, 44, 47, 48, 50, 51, 52, 54, 56, 57, 58, 59, 60, 62, 63, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 83, 84, 86, 87, 88, 90, 92, 93, 94, 96
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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What is the limit of a(n)/n?
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LINKS
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EXAMPLE
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a(5)=9 since 9 is not equal to 2*a(k)+1 nor 3*a(k)+1 for 1<=k<5; and since 9 is allowed to be present, then 19(=2*9+1) and 28(=3*9+1) are to be excluded.
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MATHEMATICA
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s = {1}; Do[u = Union[s, 2s + 1, 3s + 1]; c = Complement[Range[u // Last], u] // First; AppendTo[s, c], {10000}]; s (* Jean-François Alcover, Dec 11 2012 *)
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PROG
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(Haskell)
import Data.List (delete)
a077477 n = a077477_list !! (n-1)
a077477_list = f [1..] where
f (x:xs) = x : f (delete (2*x + 1) $ delete (3*x + 1) xs)
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CROSSREFS
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KEYWORD
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easy,nice,nonn
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AUTHOR
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STATUS
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approved
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